Air-Fuel Metering for Internal Combustion Reciprocating Engines

ABSTRACT

A fuel metering system for an internal combustion engine having a fuel injection timing unit to indicate a timepoint during one or more engine strokes, a fuel metering element have a predetermined full stroke volume for metering fuel into an air-fuel mixing location during one or more of the engine strokes, and a fuel metering element controller to control the delivery of fuel by causing the fuel metering element to deliver one of a full stroke volume and a fraction of a full stroke volume to achieve a desired AFR. In some embodiments, power generator circuitry is provided to harvest power from the ICE to power at least one of the fuel injection timing unit, the fuel metering element, and the fuel metering controller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 17/033,661, filed Sep. 25, 2020, which claims the priority benefitof U.S. Provisional Application Ser. No. 62/906,701, filed Sep. 26,2019. This application claims the priority benefit of both of theforegoing applications, which are each hereby incorporated by referencein their entirety.

TECHNICAL FIELD

The present invention relates to the field of air and fuel metering atthe induction (i.e., intake) of internal combustion engines. Moreparticularly, it involves improved fuel metering systems and methods toensure efficient metering, mixing, and combustion of fuel and air ininternal combustion engines (ICEs).

BACKGROUND OF THE INVENTION

ICEs typically use a reciprocating piston in a combustion chamber wherecombustion of oxygen and fuel mixtures occurs. The expansion of gasesduring the combustion cycle is then used to drive the piston to convertthe chemical energy of combustion into mechanical energy. Many technicaltasks and subsystems are involved in the operation of ICEs. The presentdisclosure is concerned with the task of mixing of oxygen and fuel inthe proper ratios or amounts to ensure controlled combustion to achieveone or more desired combustion goals (e.g., minimizing undesiredpollution or inefficient combustion, maximizing power, or maximizingfuel efficiency).

Proper mixing of oxygen and fuel is a key technical requirement forinternal combustion engines, regardless of the combustion goal. Thespeed, efficiency, and extent of combustion depends on mixing oxygen andfuel in the proper ratios. As used herein, references to air may be usedinstead of oxygen in the combustion process or combustion ratios,although it should be understood that the combustion process involvesthe reaction of only the oxygen in the air with the fuel. Forconsistency, references to ratios of fuel-air mixtures will be expressedas that of the air-to-fuel ratio (AFR). It will be understood, however,that persons of skill in the art may apply the teachings of thedisclosure provided herein using the inverse relationship of thefuel-to-air ratio (FAR).

If the combustion mixture consists of too great a proportion of fuelrelative to oxygen (also referred to as an “excess” or “rich” AFR ormixture), the combustion will be slow and/or incomplete, resulting inreduced power output, excess pollution, or both. The excess fuel doesnot fully combust inside the chamber, resulting in continued burning ofthe fuel in the exhaust process, resulting in waste heat that creates noengine power as well as increased emissions of unwanted solids (soot)and organic compounds. With an extreme excess of fuel in the air-fuelmixture, the engine will no longer support combustion and will cease torun. There are benefits of operating with a slight excess of fuel in theair-fuel mixture, however. Maximum power output is achieved with aslight excess of fuel, and results in overall lower engine temperatures,with the excess fuel serving to remove heat from the combustion process.

An excess of oxygen or air (also referred to as a “deficit” or a “lean”AFR or mixture) results in reduced power output. With an extreme deficitof fuel in the mixture, the ICE will no longer support combustion andwill cease to run. However, as with excessive or rich AFRs, there arealso benefits in running an ICE under a slight fuel deficit: emissionsof exhaust gas pollutants are reduced because the fuel is completelyconsumed during the combustion step, with no fuel wasted in the form ofunburned hydrocarbon gases or soot. Accordingly, maximum fuel efficiencyis achieved when operating under a slight fuel deficit (i.e., a slightlylean AFR). However, as fuel deficits continue beyond the maximumefficiency point (i.e., as the AFR continues to increase), before theICE ceases to run altogether it suffers negative effects of increasednitrogen-oxide pollutant emissions and poor running characteristics suchas misfiring/stumbling, ultimately resulting in loss of combustion.

The conditions of an exactly correct fuel and oxygen mixture to resultin chemically-balanced oxidation/combustion is referred to herein as astoichiometric mixture. As previously stated, conditions of excess fuelin the mixture are referred-to as rich or excess mixtures or AFRs; andmixtures with a deficit of fuel in the mixture are referred-to as leanmixtures or AFRs. Rich mixtures may equivalently be referred to as thoseinvolving a high FAR or a low AFR. Similarly, lean mixtures are thoseinvolving a low FAR or a high AFR.

In one aspect, the present disclosure provides exemplary methods for thecombustion of gasoline fuel when mixed with atmospheric air in ICEs.Given these two chemical inputs to cause a combustion reaction, thereexists particular ratios of air and fuel which constitute rich,stoichiometric, or lean mixtures. The use of these particular inputs asexamples for the purposes of describing and exemplifying the inventionin the following descriptions are nonlimiting, and the methods disclosedherein may be used to enact different ratios should a different ratio beadvantageous for use of different chemical fuels and oxidizers (e.g.,fuels other than gasoline or other hydrocarbons, and oxidizing agentsother than air such as pure oxygen).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing power output and fuel efficiency for aninternal combustion engine.

FIG. 2 is a functional system diagram illustrating aspects of prior artelectronic fuel injection systems.

FIG. 3 is an illustrative representation of one embodiment of a methodto determine the amount of air inducted into a combustion chamber of acylinder of an internal combustion engine.

FIG. 4 is a graph illustrating power output, IdPI values, and the ratioof pump pulse width to IdPI values as a function of the air-to-fuelratio (AFR) in an internal combustion engine according to one embodimentof the invention.

FIG. 5 is a simplified schematic diagram of a fuel metering system andinternal combustion engine according to an embodiment of the invention.

FIGS. 6A and 6B are cross-section diagrams illustrating a Micro-meteringLow-pressure Pump (MLP) according to one embodiment of the presentinvention.

FIG. 7 is an example circuit and system configuration diagramdemonstrating a method for passively activating fuel delivery even inthe absence of power or logic control upon startup, according to anembodiment of the invention.

FIG. 8 is a flow chart illustrating a method of controlling theoperation of an internal combustion engine at a desired AFR according toone embodiment of the invention.

FIG. 9 is a flow chart illustrating a method of determining a maximumpower AFR fiducial for a running ICE according to an embodiment of theinvention.

FIG. 10 is a flow chart illustrating a method of determining a maximumfuel-efficiency AFR fiducial for a running ICE according to anembodiment of the invention.

FIG. 11 is a graph illustrating a relationship between the IdPI measuredmetric and a prescribed fuel output variable according to one embodimentof the invention.

SUMMARY

In one embodiment, the invention comprises a method of controlling theair-fuel ratio (AFR) of an operating internal combustion engine (ICE),the ICE having a combustion chamber, at least an intake stroke and acombustion stroke, a speed controller to adjust a throttle to maintain atarget rotational speed, and an air intake determination unit todetermine an air intake parameter indicative of the amount of airinducted into the combustion chamber during an intake stroke, the methodcomprising: a) determining a maximum-power AFR fiducial by 1) operatingthe ICE under a constant load at a first AFR defining one of a richmixture and a lean mixture; 2) decreasing the AFR and determining achange in engine power output in response to the decrease in AFR; 3) ifthe engine power output increases in response to the decrease in AFR,repeating step a2 until the engine power output decreases in response tothe decrease in AFR; 4) if the engine power decreases in response to thedecrease in AFR in step a2, increasing the AFR and determining a changein engine power output in response to the increase in AFR; 5) if theengine power increases in response to the increase in AFR in step a4,repeating the step of increasing the AFR and determining a change inengine power output in response thereto until the engine power decreasesin response to an increase in AFR; and 6) identifying the maximum-powerAFR fiducial as the AFR at which any change in AFR results in a decreasein the power output of the engine; b) determining a maximum-efficiencyAFR fiducial by 1) operating the ICE at a constant load at a second AFR,and determining the absolute amount of fuel injected for each air-fuelintake stroke; 2) increasing the AFR and determining a change in theabsolute amount of fuel injected for each air-fuel intake stroke at theincreased AFR; 3) if the absolute amount of fuel injected for eachair-fuel intake stroke decreases in response to the increase in AFR,repeating step b2 until the absolute amount of fuel injected for eachair-fuel intake stroke increases in response to the increase in AFR; 4)if the absolute amount of fuel injected for each air-fuel intake strokeincreases in response to the increase in AFR in step b2, decreasing theAFR and determining a change in the absolute amount of fuel injected foreach air-fuel intake stroke in response to the decrease in AFR; 5) ifthe absolute of amount of fuel injected for each air-fuel intake strokedecreases in response to the decrease in AFR in step b4, repeating thestep of decreasing the AFR and determining a change in the absoluteamount of fuel injected for each air-fuel intake stroke until theabsolute amount of fuel injected for each air-fuel intake strokeincreases in response to a decrease in AFR; and 6) identifying themaximum-efficiency AFR fiducial as the AFR at which any change in AFRresults in an increase in the absolute amount of fuel injected; and c)operating the ICE at a desired AFR by controlling the amount of fueldelivered into the combustion chamber for each air-fuel intake stroke toachieve the desired AFR based on one of interpolation between themaximum-power AFR and the maximum-efficiency AFR, and extrapolation fromone of the maximum-power AFR and the maximum-efficiency AFR.

In one embodiment, the invention comprises a method of controlling theair-fuel ratio (AFR) in an operating internal combustion engine (ICE),the ICE having a speed controller and an air intake determination unitto determine an air intake parameter indicative of the amount of airinducted into the ICE for each fuel-air intake stroke, the methodcomprising: a) characterizing at least a portion of the powerperformance of the ICE by 1) operating the ICE at a constant load at afirst AFR; 2) performing a series of stepwise changes in the AFR andoperating the ICE at a constant speed for a plurality of combustioncycles at each AFR setting in the series of stepwise AFR changes,wherein the series of AFR settings includes rich AFR values at which theICE experiences poor engine performance, rich AFR values at which theICE experiences good engine performance, and lean AFR values; 3) foreach AFR setting in the series of AFR settings, determining a poweroutput of the ICE at the AFR setting based on a power outputdetermination for at least a subset of the plurality of fuel-air intakecycles at the AFR setting; b) determining at least one of amaximum-power AFR fiducial and a maximum-efficiency AFR fiducial; c)operating the ICE at a desired second AFR based on the maximum-power AFRfiducial and the power output of the ICE in the region of the desiredsecond AFR.

Illustrative embodiments of the invention are described herein. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. In the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the design-specific goals, which will vary from oneimplementation to another. It will be appreciated that such adevelopment effort, while possibly complex and time-consuming, wouldnevertheless be a routine undertaking for persons of ordinary skill inthe art having the benefit of this disclosure.

Certain terms are used throughout the following description and refer toparticular system components. As one skilled in the art will appreciate,components may be referred to by different names. This document does notintend to distinguish between components that differ in name but notfunction.

FIG. 1 illustrates an exemplary graph of an ICE output power vs AFRcurve 110 and a fuel efficiency vs AFR curve 120. Both curves 110, 120demonstrate that inaccurate mixing (too much or too little fuel) resultsin rapid loss of both power and fuel economy. Beyond these operatingzones, the engine ceases to run altogether. FIG. 1 is discussed ingreater detail below.

The challenge of providing a burnable air-fuel mixture in an operating(i.e., running) ICE is complicated by the rate at which the induction orignition process occurs, which is typically not less than 30 combustionevents per second, and the fact that the amount of air and fuelinduction may vary widely in successive individual combustion eventsdepending on a number of factors including at least: instantaneousengine load; acceleration or deceleration requests (i.e., increasing ordecreasing the throttle); varying environmental hindrances to airinduction; varying propensity for the liquid fuel to vaporize based onfactors such as fuel age, constituents, composition, or temperature;varying air constituents or composition influenced by temperature,humidity, air pollutants, and altitude; and varying engine inductionperformance based on wear, temperature, operating regime, andmanufacturing variations.

The historic means of providing a burnable air-fuel mixture in an ICE isby the well-known means of a carburetor. Carburetors are mechanicalsystems having chambers and/or conduit structures for receiving air andfuel and mixing them so as to ensure a combustible mixture under mostconditions. Carburetors provide a restriction structure in the airflowpath which causes the induction air velocity to increase (thusdecreasing the local pressure via the Bernoulli equations), andsituating a fuel nozzle at the zone of lower pressures and highervelocity. Because of the decrease in air pressure at the restrictionpoint in the air induction line, fuel (typically at a higher pressure)is pulsed into the induction air stream in proportion to the airvelocity (which is used as a proxy for air volume or amount, therebyproviding a basis for determining the AFR) entering the induction step.The pressure necessary to ensure that adequate fuel is delivered andmixed with the air is typically provided by gravity and atmosphericpressure, and the process is a continuous one that does not involveactive measurement of the air and fuel delivered on a particulartimescale or per combustion event to precisely control the AFR.

Carburetors are complex mechanical structures, requiring eloquent andhigh-tolerance manufacturing of multiple mechanical fluid circuits inmetal housings. Maintaining physical geometries in the carburetor areparamount to attaining consistent, combustible air-fuel mixtures.Carburetors may contain dozens to hundreds of separate parts. The largenumber of components, material and process-tolerance requirements, aswell as the multiple-steps necessary to construct mechanical fluidcircuits in a physical housing result in high manufacturing costs.Moreover, the tight-tolerance physical structures and small orificesutilized cause carburetors to be prone to frequent fouling whencontaminants are present. This can sometimes occur based on aircontamination alone, but is more frequently the result of obstruction orblockage of the smaller mechanical fluid circuits when contaminants arepresent in liquid fuels. Worse, as fuel ages, the lower molecular weightcomponents typically evaporate faster, causing the concentration ofhigher molecular-weight components in the fuel to increase. As thisprocess continues, the fuel itself becomes more viscous and maytransform into sludge or solids which clog the small mechanical fluidcircuits, causing the carburetor to fail and the ICE to be inoperative.When the carburetor fails, because of its complexity and location deeplyand tightly integrated into the ICE systems, repairs are often beyondthe capability of most users, who must dispose of the ICE or pay costlyservice fees.

The fuel degradation process outlined above is accelerated by inherentdesign characteristics of carburetors, which require at least one—andusually two or more—openings to the atmospheric air. Since gasoline fuelvaporizes readily, these open channels to the air drive the foregoingfuel degradation process, resulting not only in fuel compromise butincreased environmental pollution. As the higher molecular weight fuelconstituents increase over time, the energy value per-unit volume offuel also decreases. Because the carburetor meters fuel based solely onfuel volume and not based on its energy value, even if the carburetorprovides combustible AFRs initially, it may become incapable ofproviding a combustible air-fuel mixture for aged fuels. Because of thecomplexity and design limitations inherent in carburetors, deteriorationand damage may occur if the ICE and fuel sit unused for as little as afew months.

The open-air requirement of carburetors also creates a particularlydangerous failure mode. If a fuel-level valve within the carburetor(called a float valve) fails to close, the entire contents of the fueltank will drain through the carburetor. This results in loss of fuel,damaging engine oil and/or the engine itself, and worst of all creatinga fire hazard in the area around the spilled fuel. This failure occursany time a particle contaminant or aged fuel prevents the fuel-levelvalve from closing. Because the float valve closing force is verysmall—usually less than 2 grams—the risk of improper valve closure incarburetors is relatively high.

Despite these drawbacks, carburetors remain in wide use because they dooffer several benefits, which includes providing for air-fuel ratiocontrol over a wide range of often rapidly changing ICE inductionconditions. Another major benefit of carburetors is their ability toprovide for air-fuel ratio control without any auxiliary powerrequirement. Thus, ICEs which utilize carburetors need not includeexternal power or batteries, and also avoid the need for associatedbattery charging systems or voltage control subsystems.

The inherent limitations of carburetors spurred the development ofalternatives for carburetors throughout the 1960s-1980s. Beginning withmechanical fuel injection, systems were developed which delivered fuelduring induction to more precisely match air intake. This evolved tobecome electronically-controlled fuel injection which completelysupplanted carburetors in American automobiles by the 1990s and remainsthe standard for automobiles today.

Electronic fuel injection (EFI) overcomes most of the weaknesses ofcarburetors, but with the detriment of increased system complexity andsignificantly increased cost. Notably, one aspect of complexity and costassociated with EFI is the need to provide electrical energy to thesystem before the ICE is running. Thus, to employ EFI with an ICE, theproduct utilizing the ICE (e.g., automobile, ATV, lawnmower, etc.) mustalso employ a power source or battery, as well as charging and voltageregulation subsystems.

FIG. 2 presents an exemplary diagram of the electrical system componentsof a motorcycle employing EFI and illustrates the complexity of thecomponents, wiring, and interactions that EFI systems employ inreplacing a carburetor. The engine control unit (ECU) 210 is thecomputerized subsystem element which monitors all the sensors, applieslogic, and commands a dose of fuel delivery for each engine cycle.

EFI systems are typically designed as either open-loop or closed-loopsystems. In open-loop EFI systems, a processor or computer searches apre-programmed look-up-table for values which match the instantaneoussensor measurements in the ICE and delivers a fuel dose that ispre-determined at the manufacturer and which should work well for thedetected conditions.

An example of a closed-loop EFI system 200 according to the prior art isshown in FIG. 2. In closed-loop EFI systems 200, one or more exhaust gassensors are often used to determine the AFR of the combustion event thatcreated the exhaust gas. Sensor measurements in EFI systems 200 caninclude a variety of sensing elements used by an ECU 210 to control themetering of fuel by a fuel pump 260 to the ICE. In the example of FIG.2, the sensors include an oxygen sensor 240 and a temperature sensor242, which monitor the oxygen concentration and temperature,respectively, of the ICE exhaust gases. Additional sensors shown in theexample of FIG. 2 include a crankshaft position sensor 244 to enable theECU to determine the timing of fuel metering events, a manifold pressuresensor 246 which is used in calculations of how much fuel is meteredinto a cylinder during an intake stroke, and a throttle position sensor248 used to deduce how much air is inducted into a cylinder duringintake strokes. It will be appreciated that other or additional sensorsmay be used in different prior art implementations. The electricalcomponents in the embodiment of FIG. 2 also include a battery 220 toprovide electrical power to the EFI system 200, and a battery chargingsystem 230. Other components such as main relay 250 may also be used toprovide electrical power to various components of the EFI system 200. Afuel pump 260, pressure regulator 270, and a fuel injector 280 are theprimary mechanical elements controlled by the ECU 200 to deliver (or“meter”) fuel to create an air-fuel mixture for combustion in thecylinders of the ICE.

In the example of FIG. 2, an oxygen sensor 240 and a temperature sensor242 may be positioned in the ICE's exhaust gas flow to sense the oxygenconcentration and temperature of the exhaust gases. The signal from theoxygen sensor is processed by the ECU 210 to determine thepre-combustion AFR based on the detected O₂ concentration andtemperature of the exhaust gas. In other words, the oxygen and/ortemperature sensor s 240, 242 indicate—after the fact—the AFR of thecombustion event that created that exhaust gas, and in particularwhether the combustion event was a rich, stoichiometric, or leanair-fuel mixture. EFI systems 200 which employ oxygen and/or temperaturesensors 240, 242 operate as a closed loop to adjust the AFR based on theactual chemical combustion performance of the ICE, and not just on theset of conditions measured by other sensors which should predict orcorrelate to combustion performance.

EFI is not used on all internal combustion engines. While EFI systemsoffer improved ICE performance relative to carburetors, their increasedcomplexity and cost prohibit their use in many applications, mostnotably small engines. Presently, EFI is primarily employed inautomotive products where the cost of the EFI system represents a smallportion of the total product cost. At present, the simplest productswhich pervasively employ EFI are high-end motorcycles. These employ thesimplest implementation of EFI, yet still impose significantly highercost and complexity than carburetors. On a motorcycle, the EFI subsystemcost is a higher proportion of total product cost than with automobiles,but the benefits of EFI may make the costs and benefits to the consumerjustifiable. Some high-end off-road vehicles are beginning to offer EFI.Small Off-Road Engines (SORE) such as used with lawnmowers, pumps,pressure-washers, generators and including handheld devicesincorporating internal combustion engines such as blowers, weedtrimmers, & chainsaws rarely, if ever, are offered with EFI. In mostcases the threshold for EFI utilization is 10% of overall product costor less. For many SOREs EFI would require increasing the price of theproduct by 60% or more, which precludes their use except in rare cases.

In order for a product to switch from using a carburetor to EFI, ingeneral the EFI implementation either must not increase total productprice by more than about 10%, or must be required by external factorssuch as government-imposed environmental, pollution control, and/orsafety regulations. The inherent architecture of existing EFI systemsinvolve complex and rapid timing events (e.g., metering multiple smallfuel doses on timescales of microseconds via components operating atelevated pressures of 2-4 atm). One object of the present invention isto provide fuel metering systems capable of providing reliable fueldelivery in internal combustion engines over a wide range of operatingconditions that are simpler and less expensive than existing EFIsystems, and which are less mechanically complex and more reliable thancarburetors.

DETAILED DESCRIPTION

In one aspect, the invention aims to provide for all the benefits ofEFI, but at system costs no more than—and preferably less than—productsusing carburetors for fuel metering. In one embodiment, the inventionprovides a system for metering air and fuel that uses software toimplement the functions of at least some mechanical elements found incarburetors. In one embodiment, systems of the present invention employnew engine state measurement metrics as logical inputs to a logic unitoperating (e.g., as software and/or firmware) in a processor such as amicroprocessor or field programmable gate array (FPGA). Systems andmethods of the present disclosure are lower in cost, simpler tophysically configure, and more accurate and reliable than mechanicalcarburetors.

In one embodiment, the invention combines the elements of fuel pump andinjector into a single subsystem which can operate at reduced pressurescompared to existing EFI systems, providing for AFR management withsignificantly reduced electrical power requirements, fewer systemcomponents, and reduced physical complexity.

In one embodiment, the invention provides an actively-managed fuel andair delivery system that is operable without the need for a power,battery, or battery charging subsystem. To further obviate the need forthese expensive electrical power subsystems, in one embodiment theinvention uses passively-actuated fuel delivery until the ICE isrunning, and energy harvested from the ICE thereafter powers theelectrical logic unit/ECU. This results in improved fuel metering vscarburetors, at similar if not lower costs.

The invention's mechanical configurations/geometries allow for reducedmechanical complexities and wide tolerances of physical features whichallow for low-cost manufacturing methods and achieving precision usingsoftware controls compared to the extremely precise tolerances requiredfor the manufacture of carburetors and conventional EFI systems.

Because systems of the present disclosure involve reduced mechanicalcomplexity, servicing the air-fuel metering system is also simplified,reducing the need for expensive maintenance.

In one embodiment, a physical housing in the general shape of acarburetor body is provided to easily integrate with existing ICEinduction, airflow, and throttle valve controls; including fuel hoseentrance, air filtering structures, and throttle linkages. In analternate configuration, a fuel metering element (FME) comprising aMicro-metering Low-pressure Pump (MLP) is placed within the fuel tank orattached to the fuel filler lid, or exists in-line with existing fueltubing to ease integration and improve accessibility compared toexisting carburetor-based ICEs.

In one embodiment, the system uses a throttle induction airflow valve inthe same way as existing carburetor or EFI systems, so that external,existing systems or components control the throttle position—includingspeed-governed throttle controls. Although it is preferred for costreasons to utilize existing throttling airflow controls, in alternativeembodiments the invention may also provide new controls for ordetections of the positioning of the throttle valve without undueexperimentation.

FIG. 3 illustrates a functional representation of a method to determinethe amount of air entering the engine's cylinder(s) using a plurality oftime-variant pressure measurements made in an air induction conduitduring an intake stroke in one embodiment of the present invention. FIG.3 provides a representation of pressure (Y-axis) vs time (X-axis), withtime proceeding to the right. ICEs follow a repeating cycle. FIG. 3represents an exemplary four-stroke-cycle internal combustion engine(‘Four-stroke’) for the sake of illustration, although the method mayalso be used with two-stroke-cycle engines without undue experimentationby a person of skill in the art having the benefit of the presentdisclosure. In a four-stroke engine, the first rotation portion, n,illustrates pressure changes in an air induction conduit during anintake stroke during the first half of the first rotation portion, and acompression stroke during the second half of the first rotation portionn. On the next rotation portion, n+1, a combustion stroke occurs duringthe first half of that rotation portion, and exhaust occurs during thesecond half. The process repeats beginning at rotation portion n+2.

The vertical axis of FIG. 3 illustrates an exemplary pressure scale. Anabsolute pressure scale is the embodiment illustrated here, althoughrelative pressures may also be used in some embodiments. The ICEpressure in the air intake conduit is initially at an environment of 1atmosphere (ATM) pressure, although the method works and in fact adaptsto varying local pressures such as high-altitude locations where thelocal environmental pressure would initially be at some pressure lessthan 1 ATM.

During the ‘intake’ phase, induction gases (e.g., air) flow in towardthe combustion chamber of the cylinder. This inflow occurs at highvelocity and within the engine's intake passageway/conduit. In someembodiments (see FIG. 5), a throttling valve (throttle) may bepositioned within the intake conduit so that induction air may beregulated (i.e., limited or unrestricted as needed) to control theamount of power the engine creates at any given time. In small off-roadengines (SORE), the throttle is most often controlled by the user or anexternal governor. Consequently, the throttle (i.e., power demand)varies independently of the air/fuel mixing system, and the mixingsystem must respond to the varying throttle conditions.

FIG. 3 illustrates pressure changes occurring in an air inductionconduit having an engineered or inherent restriction to determinepressure changes during a plurality of engine rotations of an ICE. Thesepressure changes are used to determine the amount of air inducted into acombustion chamber of a cylinder according to an embodiment of theinvention. More particularly, the figure provides a graph 300 ofpressure changes (Y-axis) over time (X-axis) during a plurality ofengine rotations 302, 304, 306, 308. Although graph 300 depicts absolutepressure over time, it will be appreciated in view of the presentdisclosure that similar graphs may be prepared to depict differentialpressure changes in the air induction conduit over time, and that theinvention may be practiced using either absolute or differentialpressure measurements.

The graph begins at time to at the beginning of an intake stroke 310,which together with compression stroke 320 occur during an exemplaryengine rotation n (302). A conventional flow restriction structure(e.g., throttle flapper) provided in the induction conduit causes apressure reduction 312 across the flow restriction during an intakestroke 310. At a plurality of timepoints (t_(n+1), t_(n+2), t_(n+3),etc.), the pressure in the induction conduit on the downstream side ofthe orifice is determined. FIG. 3 illustrates a method to determine arepresentative measure of the area under the pressure-time curveaccomplished by summing or integrating the values of pressure vs. time,as illustrated by the shaded regions 314, which here illustrate themathematical product of pressure and the duration of each time period.For example, pressure P_(n) is taken as representative of the absolutepressure for the time period between the beginning of the intake strokeat to and the pressure at timepoint t_(n+1). Similarly, the pressureP_(n+1) is taken to represent the absolute pressure of the time periodbetween timepoints t_(n+1) and t_(n+2). Similar pressure values arelikewise calculated for each of the remaining periods comprising theintake stroke, and the values of these are mathematically integrated inorder to arrive at a mathematical value indicative of the area under thepressure-time curve for at least a portion of the intake strokes. Itwill be appreciated that some amount of imprecision is introduced at lowsampling speeds, and these are improved with higher sampling speeds. Ithas been demonstrated that sampling every 200 microseconds is sufficientto achieve accurate air volume determinations at 7000 rpm, and thissampling rate is easily accomplished by the most affordablemicrocontrollers. It will be appreciated that the absolute meaning ofthe resulting accumulated value need not be tied to existing units ofmeasure, but that the resulting mathematical value is a representativevalue which is reliably changing and correlates to the volume of airinducted to the engine during an intake stroke, and which may be used todetermine the proper amount of fuel to be metered for a particular ICEin which a system according to the present invention is implemented. Itwill be apparent to a person skilled in the art that multiple means ofmathematically correlating the air intake volume given the pressuresensor data over time are possible, and the methodology described hereis to be considered nonlimiting.

The difference between the pressure at the start of the intake stroke,illustrated by dotted line 316, and each of the sampled pressures (Pn,Pn+1, Pn+2, Pn+3, etc.) for the time periods comprising the intakestroke 310 may be summed or integrated to provide a measure of the airinducted into the combustion chamber during the intake stroke 310. Thissummed parameter may be calculated by a processor, and is referred toherein as an induction change in pressure integration (IdPI) value. Aswill be appreciated, the greater the number of periods into which theintake stroke is divided, the greater will be the accuracy of thecalculated IdPI value for a given intake stroke (e.g., 310, 350). Afterthe intake stroke 310 is complete, there is no air flowing into thecylinder combustion chamber during the following compression (320),combustion (330), and exhaust (340) cycles, so the pressure for thosestrokes is the same as that at the start and end of the intake stroke310, as illustrated by the solid pressure line in FIG. 3.

Intake stroke 310 is illustrative of an intake stroke for which intakethrottle valve highly restricts air flow into the induction conduit, forexample, when the ICE is on idle and takes in very little air. For thisreason, the decrease in pressure is relatively high once air begins toflow in the induction conduit, as indicated by the depth of the pressuredecrease 312. In contrast, intake stroke 350 occurring during awide-open throttle, has a comparatively small pressure decrease 352,because the throttle provides relatively little restriction to the flowof air into the combustion chamber of the cylinder. FIG. 3 furtherillustrates a second compression stroke 360 following intake stroke 350.Compression stroke 360 is similar to compression stroke 320 previouslydiscussed.

In one embodiment the method of determining air induction into acylinder may be implemented by an Induction Change in PressureIntegration (IdPI) unit provided as part of an air inductiondetermination unit (AIDU). The AIDU may include a pressure sensor tosense absolute or differential pressure during an intake stroke. Thepressure sensor may sense pressure continuously or at a desired samplingrate (e.g., at a desired sampling rate of 100-1,000,000 times per secondor more). The IdPI unit preferably either receives pressure signals at adesired rate from the pressure sensor, or samples a continuous signalfrom the pressure sensor at the desired sampling rate, and thencalculates an IdPI value as described in connection with FIG. 3 that isindicative of the amount of air inducted into the cylinder combustionchamber during the intake stroke.

The IdPI unit may be implemented as a logic unit within the AIDU, andmay comprise a non-transitory computer readable medium storing code forexecution by a processor to receive and process the pressure changes andcalculate air inducted. In one embodiment, the IdPI unit measurespressure changes during each intake stroke in an induction conduit at alocation between an intake valve of a cylinder combustion chamber andthe throttle induction airflow valve. The IdPI unit provides a signalindicative of the mathematical area under the curve of pressure overtime, measured for each air intake stroke. The integrated area under thepressure curve for each stroke changes in proportion to the amount ofair which entered the ICE on each stroke. A mathematical relationshipbetween the IdPI value and the amount of air which entered the ICE isused to determine the amount of fuel which must be delivered in order toachieve the target air-to-fuel ratio (AFR).

In some embodiments, the pressure signal and/or the IdPI value in thetime domain may be utilized to determine which engine rotation (orportion of a rotation) corresponds to an intake stroke, and to derivetiming of engine events such as shaft rotation and rpm. In alternativeembodiments, existing ICE electronic signals from, e.g., a camshaftposition sensor, a crankshaft position sensor, an engine output shaftposition sensor, or other timing signals indicative of engine timingevents may be used to determine when an intake stroke occurs (e.g., byidentifying one or more timepoints at the start, induction phase, and/orend of an intake stroke). In some embodiments, with knowledge of theIdPI values and ICE rpm, the load (i.e., the amount of work that theengine is performing) may be derived without the need for sensorscoupled to the engine's output or on the engine's exhaust.

When the throttle valve is almost completely closed, commonly referredto as “idle,” the engine is only producing enough power to maintain itscommanded idle speed. The throttling valve prevents almost all air fromentering the combustion chamber, and very little chemical and mechanicalenergy is produced. The challenge for the air/fuel metering system is todeliver an amount of fuel in proper proportion to the amount of air(more specifically oxygen) that entered the cylinder via the intakeconduit to achieve a target AFR. FIG. 3 illustrates a method ofdetermining the amount of air entering into the combustion chamberaccording to one embodiment of the present invention.

The method may be performed by an air induction determination unit(AIDU) comprising a processor having a logic unit capable of processingpressure signals from a pressure sensor in the air intake conduit aplurality of times during an intake stroke (e.g., intake stroke 310).Thus, the AIDU has the ability to track time and to measure pressure. Inparticular, an induction change in pressure integration (IdPI) unitrepeatedly determines pressure at various timepoints during an inductionstroke, and computes an area under the time-variant curve of pressure.In a preferred embodiment, the IdPI unit determines pressure as manytimes as practicable, and only during the intake stroke portion of thecycle, although in alternative embodiments the area may be calculatedusing any number of intervals and also by calculating area underadditional portions of the engine cycles (e.g., the area under the curvefor an entire engine rotation, whereas the intake stroke only appliesfor a half-rotation) so long as the computed value may be relatedmathematically to the amount of air ingested during intake strokes.

As illustrated, intake strokes (310) for the idle condition—orthrottling valve mostly-closed condition—results in less accumulatedarea (shaded area) under the pressure-time curve than the accumulatedarea under the condition of ‘Wide-Open/Max-Power Throttle Position’(WOT) 350. Because there is very little airflow restriction beingenacted by the throttling valve during the n+2 (WOT) rotation, thepressure at the engine's intake remains at, or very close to,atmospheric pressure. It will be understood that the pressure inside theinduction conduit remains at the local atmospheric pressure for all butthe intake stroke, regardless of the position of the throttling valve.This is because the air intake valve (523, FIG. 5) remains closed exceptduring intake strokes, thereby preventing air flow in the inductionconduit and into the cylinder during all other strokes (e.g.,compression, combustion, exhaust). In the absence of air flow across thethrottling valve, the pressure on either side of the throttling valveremains at the local environmental pressure. The IdPI unit and method offinding the area under the pressure-time curve is referred-to herein asInduction Change in Pressure Integration (IdPI), denoting the method ofintegrating (I) the changes of pressure (dP) over time within theengine's induction (I) circuit.

The IdPI metric is influenced by the rate at which air is entering theengine. To illustrate: in the case that the throttling valve is almostclosed, when the engine's piston is causing the rate of filling thechamber to be very fast (e.g., when engine RPM is high), the IdPI sensorwill experience the maximum pressure drop (Pn+3 in FIG. 1) andconsequently the total volume of air which resultantly gets into thecombustion chamber will be limited. Conversely for the samealmost-closed throttling valve setting, if the engine RPM is low andthus air is barely flowing, the pressure measured by the IdPI sensorwould be practically indistinguishable from the surrounding atmosphericpressure and yet the total volume of air which resultantly gets into thecombustion chamber will be maximal. Thus, in order to ultimately deducethe amount of air which entered the combustion chamber for the purposesof prescribing a corresponding dose of fuel, in one embodiment the IdPIunit applies a transform metric using the IdPI value and a velocitymetric (e.g. RPM) to determine the volume of air that entered thechamber using a pre-determined relationship. In a preferred embodiment,a mathematical equation defining the IdPI value vs necessary fuel doseis defined for a given engine rpm, and the variables (such as offsetsand slopes) are adjusted based on the engine RMP. In alternativeembodiments, look-up tables (e.g. fuel MAPs known in the art) may beused in lieu of complex, multi-variable mathematical equations.

Various methods to integrate the pressure-time curve will be apparent topersons of skill in the art having the benefit of the presentdisclosure, and the example given in FIG. 1 is to be considerednonlimiting.

In one aspect, the invention comprises a fuel metering element (FME)such as a micro-metering low-pressure pump (MLP) whose volumetric outputcan be controlled using a low-power, switchable signal. In a preferredembodiment, the FME is a diaphragm MLP pump actuated linearly. In aparticular embodiment, the linear activation in a first (e.g., forward)direction is achieved via an electromagnetic pulse signal. Theelectrical pulse width and/or amplitude of such electromagnetic pulsesignals are signals easily controlled by low-cost logic controllers. Thelinear activation in the other (e.g., second or reverse) direction ofthe fuel-pumping stroke may be achieved via passive means (e.g., springreturn) or by actively reversing the direction of the electromagneticpulse using a low-cost fuel metering element controller (e.g., amicroprocessor or field programmable gate array (FPGA)).

In one embodiment, an electromagnetic pulse signal may activate the FMEto cause it to deliver either a full stroke volume of fuel or anydesired partial stroke volume of fuel. A FME controller may be providedto control one or both of the duration and amplitude of theelectromagnetic pulse signal to the FME. If the FME controller allowsthe full electromagnetic pulse to actuate the FME, a full stroke volumeof fuel is provided, which in a particular embodiment is a volume offuel sufficient to provide a rich, combustible volume of fuel understartup conditions. The FME controller may include circuitry to switchoff the electromagnetic pulse at any point during the delivery of astroke volume of fuel so as to achieve any desired portion of a partialstroke volume (e.g., any value from 0-100% of the full stroke volume).The FME controller may either reverse the polarity of the signal andcause the pump to move in the opposite direction, or may simply shuntthe power and allow a biasing element to return the pump to the initialposition prior to the next intake stroke.

With knowledge of the air inducted during each intake stroke (e.g.,using an air induction determination unit having an IdPI unit), and theability to control the metering of fuel, systems of the presentinvention may control the fuel metering to achieve a desired goal ortarget AFR. In one embodiment, a fuel injection timing unit detects (orotherwise identifies) the occurrence and timing of an induction stroke,and provides a timing signal to the FME controller, which may provide adesired amount of fuel to achieve a target AFR based on the magnitude ofthe air inducted into the cylinder during one or more immediatelypreceding intake strokes.

Because the air induction and fuel metering steps for a singlecombustion event occur simultaneously (i.e., during a single intakestroke), it is impossible to use the air induction for a singlecombustion cycle, calculated using the IdPI as discussed above, as thebasis for calculating and delivering a desired amount of fuel for thesame combustion event/intake stroke. However, under steady-stateconditions at constant load, or under any condition of rapidly repeatingcombustion cycles, the rate of change for any throttle differences iscomparatively very slow. Accordingly, the amount of air induction forsuccessive intake strokes is practically unchanged from one stroke tothe next, so that the air induction for a first intake stroke of a givencylinder can be used to determine and deliver the amount of fuel to bedelivered in a second, immediately succeeding intake stroke for thatcylinder. Accordingly, in one embodiment the amount of air inducted fora first intake stroke is calculated by the IdPI unit within the AIDU andused to determine and control the amount of fuel to be injected for thenext (i.e., immediately succeeding) combustion cycle for a particularcylinder. It will be noted that such calculations may be performedseparately to control the amount of fuel in each of a plurality ofcylinders (e.g., eight such calculations for an eight-cylinder engine).

In another embodiment, a measure of central tendency of the air inductedfor a series of intake strokes for a particular cylinder (e.g., a singlecylinder of a single-cylinder ICE or a specific cylinder of amulti-cylinder engine) is calculated by the AIDU and IdPI units and usedto determine the amount of fuel to be delivered to the combustionchamber in a succeeding intake stroke. For example, in one embodiment amoving average of the air inducted into a cylinder in a series of 10intake strokes may be used to determine the amount of fuel to bedelivered in an 11^(th) intake stroke immediately following the 10intake strokes used to calculate the moving average. The use of measuresof central tendency may provide for more consistent delivery of fuel bysmoothing the data for the calculated air induction amounts. It will beapparent that moving averages using different numbers of strokes (e.g.,2, 3, 5, 7, 15, 20, 100, etc.) may be used instead of 10. In alternativeembodiments, different measures of central tendency (e.g., a medianvalue, or a percentile value of all of the calculated values of airinduction for the plurality of intake strokes, e.g., the 40^(th)percentile, the 75^(th) percentile, etc.) of the air inducted for anydesired number of intake strokes may be calculated and used to determineand control the amount of fuel to be delivered in a succeeding (e.g.,the next) intake stroke to achieve a desired AFR.

In one embodiment, the desired amount of fuel is a stoichiometric amountof fuel (i.e., an amount of fuel to achieve an AFR of 14.7) isdelivered, based on an amount of air inducted for one or more precedingevents as calculated by the IdPI. In another embodiment, the desiredamount of fuel is a rich mixture (i.e., greater than a stoichiometricamount of fuel, e.g., sufficient to achieve an AFR of less than 14.7,such as 12.6, which is the maximum power AFR). In a still furtherembodiment, the desired amount of fuel is a lean mixture (i.e., lessthan a stoichiometric amount of fuel, e.g., an AFR greater than 14.7,such as 15.0). In various embodiments, the desired amount of fuel may beselected by a user, or algorithms may be provided in one or morecontrollers to cause the fuel metering system switch between astoichiometric mixture, a rich mixture, and a lean mixture based onprogrammed parameters such as acceleration or deceleration requests,load, atmospheric temperature or pressure, humidity, engine temperature,running time, or based upon inputs received from system monitoringsensors.

In a preferred embodiment, the FME actuation pulse for delivering fuelto the combustion chamber for a particular intake stroke is supplied bythe act of a permanent magnet associated with the engine's flywheelmoving quickly past an electromagnetic-generator pickup coil, asexplained in greater detail below in connection with FIG. 5. Thisconfiguration already exists in small off-road and handheld engines asthe manner that the electrical spark is generated. In one embodiment,the magnet moves past a pickup coil (e.g., the spark system's existingpickup coil) and generates an electrical pulse which drives the FME andcauses a squirt of fuel of a desired amount to be delivered upon thevery first engine rotations, and even before the logic controller ispowered and has a chance to boot its operating software. Because startuprotation behavior can be accurately characterized for any given ICE,fuel metering systems of the present invention may be sized to passivelyharvest energy from the flywheel (or other passive sources such aspneumatic or mechanical events within the ICE) and cause the FME todeliver a rich, combustible AFR mixture to the cylinder during eachstartup intake stroke. In one embodiment, the permanent magnet, pickupcoil, and MLP are sized in consideration of each other such that awholly passive pulse results in a squirt of fuel equating to the mostfuel-rich fuel-dose-per-stroke of all operating regimes (e.g., therichest mixture at which the engine is capable of operating, whichgenerally occurs during startup). In this way, the engine may be dosedwith fuel sufficient for reliably starting and running, albeit withoutusing the IdPI and associated logic to actively determine the amount ofair inducted and the amount of fuel to achieve a desired AFR duringstart-up.

In one embodiment, after a specified number of rotations (e.g., about 4rotations), enough electrical charge will have been harvested and enoughtime elapsed to allow controllers and/or processors in the system toassert active AFR metering. In particular, when the FME controller isoperating, it may use the IdPI to determine of the amount of airinducted in one or more intake cycles to determine the amount of fuelneeded for subsequent pulses to achieve a desired AFR. This may involveactively shunting a portion of the passively-generated activation pulsein order to cause the MLP to provide less than a full stroke volume fuel(which as noted may be a rich mixture of fuel) to affect a leanermixture. The timing at which the shunting signal is sent may also becontrolled for each engine intake stroke to achieve a desired AFR (e.g.,a stoichiometric mixture).

In one embodiment, the system includes energy storage elements (e.g.,one or more capacitors) to store energy from the pickup coils and thenuse this stored energy to drive processors and logic unit controllingthe FME (e.g., a MLP or controllable valve) to meter fuel for eachintake stroke. In alternative embodiments, batteries and chargingsystems or other power supplies may be provided.

Once the ICE has been started and energy from the spinning enginesufficient to boot and power the logic controller has been harvested, alogic unit (e.g., implemented as part of a fuel metering element (FME)controller), may then cause the engine to produce warm-up andacceleration enrichment AFR levels according to methods known in the artprior to performing AFR control methods of the present invention.

In one embodiment, an FME controller monitors engine conditions forindicators of a steady state and a stable load. These may be provided bytorque sensors, monitoring output of the associated equipment (such aselectrical output of generators), monitoring the fuel delivery output,monitoring IdPI in a preferred embodiment, measuring thestroke-to-stroke time difference of intake and power strokes, etc. Insome embodiments, existing electrical signals available from controllersalready present in the ICE may be used by the FME controller todetermine when the engine is operating at a steady state and a stableload.

A four-stroke-cycle engine performs one rotation portion consisting ofan intake/induction half followed by a compression second half; and asecond rotation portion consisting of an explosion/combustion first halffollowed by an exhaust second half, as previously described in thediscussion of FIG. 3. In this description, the ICE movement during thefirst rotation portion is provided by the momentum stored in the movingcomponents. In the second rotation portion, the engine movementaccelerates during the explosion half-stroke and decelerates during theexhaust half-stroke. If an ICE is subject to a LOW level of constantload, then the first rotation portion will show a low magnitude ofslow-down/deceleration which occurred due to energy losses in the engineand the work being done externally by the engine. Conversely, if the ICEis subject to a HIGH level of constant load, then the first stroke willshow a higher magnitude of slow-down/deceleration due to the externalwork that was done while the engine stroke was only coasting.

In order for the ICE to maintain an overall average speed, the amount ofslow-down which occurs during the coasting/slowing phases of the enginecycles must be matched with acceleration/speed-up caused by thecombustion cycle. These may be detected with a single monitoringposition with a four-stroke-cycle engine, but must include two or moremonitoring positions with a two-stroke-cycle engine. With the ability tomeasure timing of each rotation of the two-rotation engine cycle (e.g.,using pick-up coils associated with the engine's flywheel), and with theability to identify which rotation constitutes the induction/compressionrotation using the timing differences or the IdPI, embodiments of thepresent invention can determine the magnitude and time-variations inengine load via mathematical relationships between these and acharacterization of the engine system.

In one embodiment, after achieving startup, active fuel metering, anddetection of steady load conditions, the invention provides a fuelmetering system capable of closed-loop AFR adjustments to maintain adesired AFR, but without the need for expensive and complex chemicalsensors in the exhaust gases typically employed in existing EFI systems.FIG. 4 is provided for reference to describe one exemplary method toachieve closed-loop AFR adjustments without a chemical sensor.

FIGS. 1 and 4 are presented with the context of all other variables insteady-state, including a constant load. FIG. 1 illustrates that maximumpower is achieved at a rich Air-Fuel-Ratio of 12.6:1 (vertical line112), as shown by the maximum-power point 115 on curve 110, and thatoutput power falls off on either side of this ratio. In mathematicalterms, curve 110 describes power as a function of AFR under conditionsof constant load, and has its maxima at an AFR of 12.6:1 (vertical line112). FIG. 1 also illustrates a stoichiometric mixture reference line130 at which the Air-Fuel Ratio is 14.7:1, and a maximum efficiencyreference line 122 at which the fuel consumption as a function of AFR isat a minima.

FIG. 4 shows graphs of several engine performance metrics as a functionof AFR. Data points for each of the 3 curves shown were obtained bymeasurements obtained on a test bench/dynamometer and exemplary ICE. Thetop-most of the three curves (410) is the relationship of the volume ofair inducted for a number of intake strokes (each data point comprisingan intake stroke), expressed as an IdPI value on the left-side Y-axis,as a function of the air-to-fuel ratio (AFR, X-axis) under conditions ofconstant load. As previously stated, IdPI values are an indicator oftotal air inducted into the cylinder during an intake stroke. Asprovided in FIG. 4, the IdPI values are sensor-reported values that arenot correlated to standard units of measure, but vary predictably inmagnitude correlated to intake air volume for intake strokes. The unitsare a result of the product of pressure and time, and areprocessor-determined values not related to traditional units of measure(e.g., atm, Pa, psi, etc.). The IdPI curve 410 has a local minima,indicated by line 412, corresponding to an AFR of 12.6:1, which meansthat the ICE is achieving the requested (constant) power despiteingesting the lowest amount of air. This can be observed from the factthat the local minimum indicated by line 412 is to the left ofstoichiometric reference line 415, located at an AFR of 14.7:1. Stateddifferently, the ICE's throttle opening was at its most-closed position,or at a setting with the least ‘request for power’ as commanded by themechanical governor whose task is to maintain a goal RPM given theprevailing load. At that AFR, the ICE is producing the most power withthe least amount of inducted air given conditions of constant load andRPM. The minima of the IdPI curve 410 occurs at an AFR of 12.6:1(X-axis) which is the AFR of maximum power.

In one embodiment of the invention, a maximum-power AFR fiducial (i.e.,12.6:1) can be identified by obtaining data points similar to those ofcurve 410 under conditions of constant load. This may be done in an ICEhaving logic unit(s) (e.g., a fuel metering element controller, airinduction determination unit, and/or IdPI unit) that causes the ICE tosweep through a desired series of AFR step changes over a desired rangeduring conditions of constant load. Data points indicative of the amountof air inducted per stroke vs. AFR (IdPI values) are obtained andprocessed to mathematically determine the minima of the IdPI curve 410.The minima of the experimentally-determined IdPI curve identifies theAFR value that requires the minimum amount of air to achieve a desiredoutput power associated with the engine speed controller (e.g., agovernor) achieving a constant RPM value under constant-load,steady-state conditions, which corresponds to an AFR of 12.6:1. Thisprocess may be used to determine a “maximum power” AFR fiducial point412 on IdPI curve 410 so that AFR deviations from fiducial 410 can beidentified as less than or greater than an AFR of 12.6:1.

Referring again to FIG. 1, in one embodiment the invention utilizes thephenomenon, shown by the minimum point 125 on the lower curve of 120,that the best fuel economy is achieved at a lean AFR value of 15.4:1,and fuel consumption increases on either side of this AFR value given aconstant load. In mathematical terms, the function describing fuelconsumption as a function of AFR has its minima (125) at an AFR value of15.4:1 (vertical line 122).

FIG. 4 also shows an X-axis relationship of AFR measured on the testbench/dynamometer to determine engine performance metrics collected withthe benefit of the present invention. The middle curve 420 illustratesthe relationship between amount of fuel delivered per pulse by a pump(as indicated by the pump pulse width on the left-side Y-axis of FIG. 4)and AFR. Curve 420 shows that this relationship has a minima,illustrated by vertical line 422) corresponding with an AFR value of15.4:1. Curve 420 shows graphically that the logic unit controlling thefuel metering element (a pump in the case of the data points comprisingcurve 420) used the smallest pumping pulse width (i.e., metering thesmallest amount of fuel) necessary to maintain the requested engine(constant) power and speed despite dispensing the smallest absoluteamount of fuel, which occurs at an AFR value of 15.4:1. This means thatthe ICE must be operating most efficiently at this setting of fuelrequired (i.e., the pump pulse width), which occurs at an AFR of 15.4:1.

Finally, the bottom-most curve of FIG. 4 depicts the ratio of IdPI andfuel output (Pump_PW in this case) as a function of AFR, and illustratesa mimima at 17-18:1 for lean burn AFR. This ratio predictably providesanother fiducial against which to derive and trim fuel mappingparameters, although the maximum-power and maximum-efficiency (i.e.,minimum-fuel) AFR fiducials are the preferred embodiment, as discussedmore fully hereinafter. By commanding the logic unit to sweep through aselected range of more or less ratio of IdPI to Pumping fuel output, theinvention mathematically finds the minima of the pumping fuel outputcurve (Pump_PW on the left chart) and thereby derives the fuel deliveryrate (e.g., pumping pulse width) which corresponds to an AFR of 15.4:1.

In one embodiment, after determining the pumping output settings whichcorrespond to maximum power (12.6:1 AFR) and maximum fuel-efficiency(15.4:1 AFR) operating points, the invention uses interpolation toprovide a pump output to achieve a desired AFR goal between thesepoints—which may include the stoichiometric AFR at 14.7:1, and usesextrapolation if a mixture outside of these known-points is desired(e.g., 11.5 or 15.5).

In one embodiment, methods of the invention can be used to determinethese maximum-power and maximum efficiency AFR fiducials even in theabsence of steady-state load and/or engine RPM conditions. This is doneby controlling input variables, then monitoring and collecting referencepoints as the engine passes through the operating zones of interest, andconstructing the one or more performance curves exemplified in FIGS. 1and 4, although the curves are constructed using datapoints collected ina non-sequential way. In one embodiment, this may be accomplished by aParameter Determination Unit within one or more logic units orprocessors. The PDU may control the engine's performance for a smalltime period (e.g., 10-60 seconds) to sweep through sufficient AFR andoperational conditions to determine fuel metering element (FME) pulsewidths that correspond to, e.g., rich, lean, and stoichiometric AFRs.

FIG. 4 can be used for illustration. The data in FIG. 4 depict thederived relationship between IdPI and fuel stroke volume (e.g.,expressed as a pump pulse width or duration) at a constant ICE load.However, there exist a plurality of other load conditions which can beexpressed mathematically as axes (e.g., z-axis, a-axis, b-axis, etc.) ina multi-dimensional space and together these multiple dimensionscomprise a surface or volume in the multi-dimensional space. WhereasFIG. 4 depicts data collected given a constant load (one slice of thez-axis is presented on the two-dimensional graph) and allowsidentification of inflection points of air and fuel within thattwo-dimensional slice of the multi-dimensional space, it is possible tocollect equivalent data at a load which is, e.g. 10% greater (anotherslice in the z-axis which would be offset in the domain of load (z-axis)by 10% from what is shown in FIG. 4). Although FIG. 4 appears as threecurves, the method only requires to observe the data, not experience itsequentially. For example, two-hundred datapoints may be observed andstored within about two seconds of ICE running, and although thesedatapoints may be observed in any order, the relationships in FIG. 4 maystill be derived. Considering the (not shown) z-axis of load in an ICEoperating in a dynamically-changing load condition, the collection ofdata (no particular data collection sequence is required) may occur anytime the ICE is operating in the loading regime(s) of interest.Accordingly, if the load conditions of an ICE are dynamically changing,then the load conditions are traveling along different load regimes(i.e., z-axis positions) of interest, and the method can account formultiple axes affecting the location of the maximum-power andmaximum-efficiency AFR fiducials, as appropriate data points (e.g.,about accumulated 2-seconds of accumulated operating time within aregime (position on a multi-dimensional axis) of interest in order toidentify the inflection points of interest to perform the AFR trimdetermination method. It will be appreciated by persons of skill in theart that the same strategies may be employed for any number ofmathematical dimensions. Although depicting data in more than twodimensions is visually challenging, the mathematical analysis todetermine maximum-power and maximum-efficiency AFR fiducials can beimplemented by persons of skill in the art having the benefit of thepresent disclosure. Such analyses are mathematically more complex thanthe two-dimensional analysis illustrated herein, and may provide greateraccuracy in fuel metering. Depending upon the implementation fordifferent ICEs the additional cost, complexity, and calculational burdenmay lead persons of skill to use the two-dimensional analysis discussedherein, or may incorporate additional axes (e.g., for load, atmospherictemperature or pressure, humidity, altitude, etc.). All suchimplementations may be implemented and are within the level of skill ofthe art with the benefit of this disclosure.

In one embodiment, the derived correlation of known sensor-and-controloperating points to one or more known AFRs is used to apply slightoffsets to the inbuilt (e.g., open loop) relationships established atthe time of manufacture when the AFRs have drifted or changedthereafter. These adaptations are employed in the form akin to the “longterm” and “short term” fuel trims, which are well known in the art,although the trim values are obtained in the present disclosure in asignificantly different manner from prior art trim values or settings.

In one embodiment, the FME controller periodically performssweeps/hunting to re-establish the long- and short-term fuel trimrelationships to contemporary deductions of actual AFR. In oneembodiment, the maximum power and maximum fuel-efficiency fiducialpoints are re-established by performing sweep routines when significantspeed, loading, environment, or temperature changes occur.

Although not required, in one embodiment the invention can be configuredto include a chemical oxygen sensor. Inclusion of this sensor wouldprovide a more direct and simple manner to deduce actual operating AFRsin real-time and thereafter apply necessary trims, but at the cost ofincreased system component counts and costs.

Turning now to FIG. 5, an illustration is provided of one embodiment ofa low-pressure electronic fuel metering (LEFM) system 500 according tothe present invention. An internal combustion engine (ICE) 520 having arotating flywheel 526 and output shaft 505 is provided. As the flywheel526 rotates, a piston 524 moves upward and downward in the combustionchamber 522. Piston 524 travels downward and intake valve 523 is openduring the intake stroke/induction cycle, drawing intake gases 502 intoproximal end 512 of the induction conduit 510. Throttling valve 518limits the airflow during the air induction/intake stroke. It istraditionally controlled by external sources (e.g., manually by a user,or automatically by a mechanical or electrical governor/controllersystem). Some embodiments of the present invention provide AFR controlwithout the need for controlling or sensing the throttle valve position,aiding the design process for a given ICE 520 implementation and keepingcosts low. In other embodiments, the throttle 518 may also be coupled toan induction change in pressure integration (IdPI) unit 540, asindicated by line 533. Interfacing the IdPI unit 540 with the throttle518 would have the benefits of faster adjustment of AFR (e.g., bycontrolling the amount of air inducted via throttle 518 or bycontrolling the operation of a fuel metering unit (FME) 550).Controlling the positioning of the throttle 518 with the IdPI unit 540would also facilitate predictive management of engine speed and loadingby coordinating instantaneous fuel metering with instantaneous airintake (e.g., throttle opening), rather than having to first detect theeffects of throttle movement, calculate an appropriate response, anddeliver the requisite fuel dose. The ability to sense and control thethrottle 518 (illustrated generally by throttle valve control line 514)is an alternative embodiment of the present invention, but since theseextra sensors and actuators add cost, a preferred embodiment omits theextra sensors and/or actuators for the benefit of low cost, with anacceptable reduction in responsiveness that could be achieved withpredictive AFR management. For ICE implementations requiring fastadjustments of AFR, air induction, and/or fuel metering, the sensorsand/or actuators may be provided.

In some embodiments, an engineered restriction (e.g., an orifice) 516may be provided in the induction conduit 510 in addition to the throttle518. The air flow limiting behavior of throttle 518 (and engineeredrestriction 516 where present) causes reduced pressure on theengine-side of the throttle 518 (and 516 where present). The pressure issensed by a pressure sensor 530 (e.g., a pressure transducer). Notably,when air is not flowing in induction conduit 510 (i.e., in all instancesexcept during the intake stroke), the pressure is the same on both sidesof the valve and is at the local atmospheric pressure, since thethrottle 518 is not fully closed during use and its purpose is to limitair flow.

Pressure sensor 530 in one embodiment senses differential pressure oneither side of the throttle 518 and engineered restriction 516 asillustrated in locations 517, 519, which would allow the system toconsider the pressure drop across any air inlet filters (traditionallyused in the art but not shown in FIG. 5). In a preferred implementation,pressure sensor 530 senses absolute pressure in the induction conduit510, with resolving power from at least 0-1.2 ATM, and is capable ofproviding updated pressure readings at a sampling rate that is at leastas fast as the Integration interval of the IdPI system. In alternativeembodiments, pressure sensor 530 may be an analog sensor. A pressuresensor 530 of the absolute-type is preferred because it allows forconsideration of other system restrictions such as air filters withvarious degrees of clogging, as well as altitude effects on airinduction more or less automatically with the IdPI method.

The signal output 535 of pressure sensor 530 is monitored by aninduction change in pressure (IdPI) 540. The IdPI unit 540 manages theIdPI calculations to determine the amount of air inducted into thecylinder during at least some intake strokes (e.g., intake stroke 315 or335 of FIG. 3). The IdPI unit 540 calculates pressure values at each ofa plurality of timepoints (e.g., time points t_(n) t_(n+1), t_(n+2))throughout an intake stroke, and integrates the pressure values toprovide an IdPI value indicative of the amount of air inducted into thecylinder during the intake stroke. The IdPI value may in someembodiments be compared to a pre-established correlation between IdPIvalues and the amount of air inducted into the combustion chamber. Insome embodiments, the IdPI value may be used directly as a proxy valueindicative of the amount of air inducted. In preferred embodiments, theIdPI unit 540 calculates the amount of air inducted into the combustionchamber for each intake stroke, although in some embodiments IdPIcalculations may be performed only for some intake strokes (e.g., tosave energy or reduce the processing burden on the processor in IdPIunit). In some embodiments, other methods and structures for measuringinducted air volume known in the art may be employed (e.g. with amass-air-flow sensor), although typically at higher cost and complexity.

In one embodiment, with knowledge of the amount of air entering thecombustion chamber 522, the IdPI unit 540 also calculates (or looks-upfrom pre-established tables) the amount of fuel that needs to becombined with the determined amount of air to achieve a target AFR goal.More particularly, the IdPI unit 540 uses a pre-established correlationbetween the IdPI value and the amount of fuel that a fuel meteringelement (FME) 550 delivers to achieve a target AFR in response to agiven IdPI value. In a preferred embodiment, the FME 550 comprises apump whose output stroke volume is determined by an electrical signal555, 557 provided to the FME from either the IdPI logic unit 540 or bystartup circuitry based on the signal from pickup coil 529, as shown byoptional control line 542. The electrical signal 555, 557 ischaracterized by a pulse width equal to or less than (preferably lessthan half of) the time of an intake stroke of the ICE 520. FME 555delivers a commanded full or partial stroke volume of fuel via a fueldelivery conduit to a fuel-air mixing location 552. Pulse width is avery easy parameter for a low-cost microcontroller to control withprecision, but the signal can be of any manner able to be correlatedwith a FME output volume. IdPI unit 540 may in some embodiments becapable of controlling or directly sensing position of the throttlevalve 518 as indicated by control line 541, and may also be coupled tothe pickup coil 529 for receiving operating power.

In a preferred embodiment, FME 550 and IdPI unit 540 are powered by theelectrical energy generated by permanent magnets 528 traveling pastelectromagnetic pick-up coils 529 situated near the engine's flywheel526. In this way, processors within the LEFM system 500 are powered withno or minimal additional components compared to ICE designs utilizingcarburetors. A further preferred embodiment captures the energy from theexisting pickup coils 529 during the exhaust/intake transition where itis typical for an engine—especially a SORE engine—to collect the energyand dump it into a spark plug despite this transition not needing aspark (a ‘wasted spark’ system). Approximately 1 W may be harvested froma typical SORE engine primary coil, so in one embodiment, IdPI unit 540and FME 550 are powered with the energy harvested from a pickup coil 529during the exhaust/intake phase of the engine cycle. While this methodof powering IdPI unit 540 and FME 550 are preferred, it will beappreciated that energy from a battery or other power supply may also beused. A further alternate embodiment is to store the energy collectedvia the pickup coils 529, such as in a capacitor, and then discharge thestored energy at a controlled interval, amplitude, and/or pulse width tometer fuel delivery from the FME 550. A still further embodimentutilizes separate or multiple coils (not shown) to harvest energy fromthe rotating engine.

A preferred Micro-metering Low-pressure Pump (MLP) 600 for use as a fuelmetering element 550 is illustrated in FIGS. 6A and 6B. Such a pump hasbeen demonstrated to be capable of controlling fuel output in responseto electrical pulse signals having pulse widths on the order ofmicroseconds. The metered output of fuel may be delivered on either sideof the throttling valve 518. If the fuel is delivered in the regionwhich undergoes pressure drops, provisions are made to account for thepressure drop's effects on fuel flow rate. This may be performed bytiming fuel delivery with consideration of the pressure swing timing asshown in FIG. 3, computationally, or by providing alternate air circuitswhich balance both sides of the pump in accord with varying inductionconduit pressures.

FIGS. 6A and 6B illustrate an embodiment of a micro-meteringlow-pressure pump (MLP) 600 according to an embodiment of the presentinvention. It will be appreciated that many other pumps known in the artmay be used to deliver fuel to achieve a desired AFR using the methodsdisclosed herein, and other methods to deliver a metered output of fuelusing MLP 600 shown in FIGS. 6A and 6B may be used in addition to themethods described herein. FIGS. 6A and 6B provide a simplifiedrepresentation of a pump design which has been demonstrated toaccomplish micro-metering of fuel in a desired quantity given a varyingpulse width input electrical signal with minimal moving parts, designsimplicity, robustness to fouling by contaminants, ease of servicing andreassembly, passively-actuated self-closure of fuel path, andmanufacturable using low cost materials and manufacturing processes.FIG. 6A shows the MLP 600 in a closed position in which no fuel ispresent (i.e., after delivering a full or partial stroke volume of fuelto an air-fuel mixing location in an induction conduit), while FIG. 6Bshows the MLP 600 in an open position in which fuel is present in a pumpchamber 630.

The MLP 600 includes an actuating element 610 which causes varyingdisplacement in a pump chamber 630 by moving a piston 620. In apreferred embodiment, permanent magnets 640, 642 having equal magneticpoles are positioned opposite each-other to cause a high concentrationof magnetic field flux to emanate outward from the interface and thusintersect the turns of an electromagnetic coil 650. In one embodiment, acore 655 comprising soft iron or similar material is provided to steerand concentrate the magnetic field flux as it intersects theelectromagnetic coil 650. In a preferred embodiment, the core 655 isomitted.

Piston 620 is illustrated as a diaphragm-type piston, but it will beappreciated that this is nonlimiting and other piston geometries may beused. Permanent magnets 640, 642 are situated so as to cause magneticfield flux lines 645, 646 to intersect the turns of electromagnetic coil650, which is shown in cross-section. Applying electrical current to thewire comprising the electromagnetic coil 650 causes electromagneticforces to interact with the magnets 640, 642 and cause movement ofactuating element 610. One-way outlet valve 660 causes fuel to flow onlyoutward from the pump chamber 630 into a fuel delivery conduit fordelivery to a fuel-air mixing location in an air supply conduit. One-wayinlet valve 670 causes fuel to flow only inward toward the pump chamber630 from a fuel source (e.g., a supply reservoir or fuel tank) and/orfuel supply conduit (not shown). As illustrated, the action of a spring680 causes the actuating element 610 to forcibly keep the valve 670closed even at times when the system is at rest or inactive. Maintainingall fuel exits closed during times of non-use is a design improvementover carbureted designs which enhances safety and reduces environmentalpollutant emissions. In one embodiment, the MLP is part of a sealed fuelmetering system with no vent or other openings to the atmosphere. Thesealed system may include a fuel supply conduit having a proximal endcoupled to a fuel source such as a reservoir and a distal end coupled tothe pump inlet valve 670, and a fuel outlet conduit having a proximalend coupled to the pump outlet valve 660 and a distal end at a fuel-airmixing location in an air induction conduit (see, e.g., FIG. 5).

Referring again to FIG. 6, the micro-metered amount of fuel is variableand controllable by the extent/deflection of actuating element 610 inevery engine cycle. With the illustrated pump 600 design, controllingelectrical pulse width and/or pulse magnitude supplied to theelectromagnetic coil 650 enables a fuel metering pump controller (notshown) to control the movement of actuating element 610 to provide anydesired fraction (e.g., 0 to 100%) of a full stroke volume (i.e., themaximum amount of fuel the pump is capable of delivering in a singlestroke or actuation event). Accordingly, a variable deflection ofactuating element 610 may be achieved for every engine cycle to providea precisely controlled, variable amount of fuel to be pumped during eachintake stroke according to the dynamic work output needed from the ICE.

FIG. 7 is an example circuit and system configuration demonstrating onemethod for passively activating a fuel metering pump 780 (e.g., MLP 600,FIG. 6) even in the absence of a separate electrical power supply orlogic control upon the engine startup sequence. A changing magneticfield dB/dt is supplied, typically by a pickup coil 710 energized bypermanent magnet 528 rotating on a flywheel 526 (FIG. 5) of a SOREengine. The changing magnetic field produces a pulsed electromagneticsignal having voltage output values over time as illustrated by graph720. The alternating positive/negative signal illustrated in graph 720may be rectified as shown at 730 to produce a signal with one voltagedirection as shown in graph 740. The cumulative total energy availableto do work is represented in graph 750. A logic unit 760 (which may bepart of or separate from the fuel metering pump controller or the IdPIunits previously described) and electrically-actuated switch 770 arepositioned such that the logic unit 760 may command the switch to closeat any time within a time frame on the order of 10-28,000microseconds—causing a shunt in the supply lines which would otherwisesupply the electromagnetic coils 750 (e.g., coil 650, FIG. 6) of thefuel metering pump 780. During the time of shunting, energy which wouldhave gone toward mechanical work of the actuating the fuel pump 780 isinstead dumped into heat of the wires and electrically actuated switch770. Connection 765 may be provided for energy harvesting to power thelogic unit 760 and/or supply a timing/detection input to the logic unit.Although FIG. 7 illustrates one method of powering logic unit 760 andproviding a timing signal, it will be appreciated that the embodimentillustrated is nonlimiting and that a variety of other methods and meansfor achieving the same functions may be provided in alternativeembodiments.

Upon engine startup, and in the case where there is no external batteryor power supply for the logic unit 760, the pickup coil 710, actuatingcoil 750, and pump 780 sizes are chosen such that in absence of anylogic unit 760, each activation of pickup coil 710 and thereafter a pumpcycle delivers a full stroke volume of fuel, in proportion to the volumeof air or oxygen in a combustion chamber (e.g., 522, FIG. 5). In apreferred embodiment, the proportion is a rich but combustible amount offuel. In alternate embodiments, the proportion is any of a combustibleproportion of fuel. In an alternative embodiment, proportion is any of acombustible proportion of fuel. In an alternative embodiment, the systemcomponents are sized such that, where logic unit 760 is unpowered, anamount of fuel sufficient for a lean but combustible mixture is providedduring startup and the logic unit then computes an additional amount offuel (beyond the lean startup stroke volume) to be delivered duringactive-control periods to achieve a target AFR.

Thus, in a preferred embodiment, upon first startup of the ICE andbefore the logic unit 760 boots software and begins controlling the fueldelivery by the pump 780, the engine receives a slightly rich AFR whichresults from a complete, un-shunted dose of electrical energy 750, 792into coil 750 of the pump. Enriched AFR is the preferred startingcondition for existing carbureted and electronic fuel injection fuelmetering systems and is also achieved with the present invention.

After the first few strokes of engine startup, when the logic unit hasaccumulated enough energy and time to boot its software, the logic unit760 begins to actively managing AFR by causing switch 770 to close/shuntthe energy at a predetermined timepoint within the fuel metering strokeof pump 780 (e.g., before all of the energy harvested by pickup coils710 from the engine coils it is delivered to electromagnetic coils 750of pump 780. Shunting the energy, as shown in graph 794 illustratingdelivery of a partial stroke volume of fuel, has the result of reducingthe metered amount of fuel in a predetermined relationship to achieve adesired target AFR. It will be recognized in view of the presentdisclosure that the area under the energy curve 794 (and thus thefraction of a full stroke volume of fuel from pump 780) may also becontrolled by other means, such as positioning an electricallycontrolled switch causing the pump-activating circuit to be disconnectedfrom the pump as a means to limit energy supplied to the pump actuatingelement (e.g., 610 FIGS. 6A, 6B), and these may be accomplished withoutundue experimentation with the benefit of this disclosure. In analternative embodiment, the un-controlled (“passive”) fuel volume thatis delivered when the logic unit 760 is not operational may be sizedsuch that a combustible yet lean (e.g., having an AFR greater than 14.7)fuel mixture is delivered, and the logic unit 760 operates by commandingthe pump to provide an additional dose of fuel greater than the passivelean volume to adjust fuel mixture to achieve a target AFR.

FIG. 7 illustrates one embodiment of controlling fuel metering without aseparate electrical power supply by passively-actuated fuel metering inthe rich regime, and when the logic unit 760 is powered and activated,the logic unit may cause an inhibition effect of theotherwise-passively-activated fuel metering down from the rich regime toincrease the proportion of air in the mixture and achieve a desiredtarget AFR. Current EFI systems must be powered and allow time for thelogic unit 760 to boot up and to stabilize sensor and software functionbefore the engine can begin to initiate combustion/running and activelycontrol fuel delivery. In embodiments of the present invention, controlof fuel delivery may occur without intervention from the logic unit 760.This behavior is referred to as passively-actuated because the acts ofcausing fuel delivery in response to engine turning occurs without needfor a pre-powered logic unit 760, and in a preferred embodiment withoutany external power sources. This is possible because thepassively-actuated elements provide fuel delivery in a state that isexcessively rich for stable engine conditions, but preferred for enginestartup. After engine starting and running commences, an active logicunit asserts fuel control authority by shunting or damping thepassively-actuated subsystem elements. This is significantly differentfrom the existing EFI paradigm. In addition, embodiments of the presentinvention may control fuel delivery and AFR using considerably lesspower than existing EFI systems, such as shunting a portion of anexisting energizing event. Benefits which arise from this paradigm arethe ability to allow engine startup without need for a power subsystemwhich removes the costs, weight, and complexities of those powersubsystems, and allows for use a smaller, lower cost logic it andswitching electronics.

Other manners of achieving the new control paradigm than as illustratedin FIG. 7 can be achieved without undue experimentation with the benefitof this disclosure, and these are considered within the scope of theinvention, which is limited only by the claims. For example, aBernoulli-type air/fuel flow delivery structure may be provided whichmeters fuel through a venturi in an excessively rich state in absence ofcontrol logic, and upon the power-up of controlling software, the logicunit may apply a flow restriction within the fuel channel via simplesolenoid or other actuator. In another example, a mechanical movingelement with one end performing mechanical work to energize amicro-metering pump and a second end placed in the vicinity of a magnetwhich moves in association with at least one of the engine's many movingcomponents. An electromagnetic structure whose circuit is passivelyshunted may be mechanically affixed to the pump's mechanical movingelement's second end such that when the magnet moves past theelectro-magnet, the counter-EMF of the shunted coil causes themechanical element to actuate completely and in a magnitude to deliver avolume of fuel sufficient to achieve a combustible target AFR. As thecontrol logic becomes powered, it may alter the magnitude of the pumpingstroke by causing a momentary open circuit of the electromagneticstructure, thus relieving some of the counter-EMF and thus delivering asmaller pump stroke and fuel dose.

In one aspect, the present invention includes methods for controllingthe air-fuel ratio (AFR) of an operating (i.e., running) internalcombustion engine (ICE). The ICE may be an engine that operates by aseries of strokes including an intake stroke and a combustion stroke,and may include a speed controller to maintain a target constantrotational speed and an air intake determination unit (AIDU) todetermine an air intake parameter indicative of the amount of airinducted into the ICE during an intake stroke.

FIG. 8 is a simplified flowchart of the steps of one such method 800 forcontrolling the AFR in an operating ICE. The method is implemented bydetermining two AFR fiducial values (maximum-power andmaximum-efficiency) while operating at steady-state conditions. The twoAFR fiducial values establish reference (fiducial) points at which theactual AFR is determined based on unchanging but observable physicalphenomena (i.e., peak power and optimum efficiency) in lieu of providinga chemical or temperature sensor in the exhaust gas as a means todetermine the actual AFR. By determining the actual AFR on an as-neededbasis, the inherent drift and imperfections of an ICE's measurement andcontrol systems may be compensated for (i.e., calibrated or trimmed) toreturn the ICE to intended and optimal performance repeatedly throughoutits service life. The two AFR fiducial values may then be used asreference points to determine how much fuel must be delivered by a fuelmetering element (FME) for each intake stroke to achieve a target AFR(e.g., 12.5:1, 13.0:1, 13.5:1, 14.0:1, 14.5:1, 15.0:1, etc.). BecauseAFR values are ratios that are always normalized such that the amount offuel is 1, AFR values may equivalently be expressed simply by the firstnumber. Thus, an AFR value of 12.5:1 may for simplicity be stated assimply 12.5, since that is the relative amount of air to a unitaryamount of fuel. The AFR fiducials may be used by one or more controllersin the system to control the amount of air and/or fuel to achieve anydesired target AFR.

The method 800 includes the step of determining a maximum-power AFRfiducial (810) at step 810. The maximum-power fiducial is anidentification of a reference point at which the ratio of air and fuelare known to be 12.6, which is the AFR value at which the ICE producesthe maximum power. The significance of the maximum-power AFR fiducial isdiscussed in greater detail above in connection with FIGS. 1, 3, and 4,and step 810 is discussed in greater detail in connection with FIG. 9below.

The method 800 also includes the step of determining amaximum-efficiency AFR fiducial at step 820. The maximum-efficiencyfiducial is a reference point at which the ratio of air and fuel areknown to be 15.4, which is the AFR value at which the ICE requires theminimum amount of fuel to achieve a target operating speed. Themaximum-efficiency AFR fiducial is also discussed in connection withFIGS. 1, 3, and 4, and step 820 is discussed in greater detail inconnection with FIG. 10 below.

Once the maximum-power and maximum fuel-efficiency AFR fiducials areknown, the amount of fuel required to achieve any other AFR value can bedetermined by a processor either by interpolation between the fuelrequired for the maximum-power and the maximum-efficiency fiducials, orby extrapolation from one of the values. Thus, the method 800 furthercomprises the step 830 of operating the ICE at a desired AFR bycontrolling the amount of fuel delivered into the combustion chamber ofthe ICE for each intake stroke. For example, calculation of the fuel tobe metered by a pump for each intake stroke at a particular throttlesetting to achieve an AFR of between 12.6 and 15.4 may be obtained byinterpolation (e.g., linear interpolation or other optimal relationshipestablished by the ICE manufacturer) between fuel required for themaximum-power AFR of 12.6 and the fuel required for themaximum-efficiency AFR of 15.4. Values below 12.6 can be calculated byextrapolation from the maximum-power AFR of 12.6, and AFR values above15.4 can be determined by extrapolation from the maximum-efficiency AFRof 15.4. In some embodiments, the method further comprises repeatingsteps 810, 820, and 830 to redetermine the fiducials and operate the ICEwhen operating conditions change (840).

FIG. 9 is a flowchart providing greater detail on the step 810 of FIG. 8on how to determine the maximum-power AFR fiducial. The method isimplemented for an ICE initially operating at steady-state, constantload conditions at some AFR (including an unknown AFR). The methodincludes the step 910 of decreasing the AFR (i.e., increasing the amountof fuel delivered per stroke relative to the amount of air), anddetermining a change in ICE power output (920) in response to the changein AFR.

If the change in output power at determination step 920 is an increase(925), the method comprises (930) again decreasing the AFR, determininga change in power output of the ICE, and repeating the decrease 930 inAFR and determination of a change in output power until the ICE poweroutput decreases in response to any decrease in AFR, and identifying themaximum-power AFR fiducial as the AFR at which any change in the AFRresults in a decrease in the power output of the ICE.

Returning to determination step 920, if the change in output power atdetermination step 920 is a decrease (927) in response to the AFRdecrease of step 910, the method comprises (940) increasing the AFR(i.e., reducing the amount of fuel delivered per stroke relative to theamount of air), determining a change in the power output of the ICE, andrepeating the increase 940 in AFR and determining a change in outputpower until the ICE power decreases in response to any further increasein AFR, and identifying the maximum-power AFR fiducial as the AFR atwhich any further increase in AFR results in a decrease in ICE poweroutput. As described in connection with FIG. 4, maximum power may beinterpreted as the setting where the requested load and rpm ismaintained yet while consuming the least volume of air—deduced byobserving the smallest IdPI per stroke and equivalently the smallestthrottling valve opening under the constant load conditions.

In some embodiments, the method further comprises (950) storing orlogging the control parameters (e.g., the fraction of a full strokevolume of fuel from a pump) provided in response to the volume of airinducted) that achieves the maximum-power AFR. When operating conditionschange during the operation of the ICE (e.g., operating parameters suchas acceleration or deceleration requests, engine load, intake airtemperature, intake air humidity, intake air pressure, altitude, enginerunning duration, engine temperature, engine rotational speed, fuelquality, or other inputs received from system status monitoring sensors,the method may include changing the target AFR to cause the fuelmetering system to switch between a stoichiometric mixture, a richmixture, and a lean mixture, or to make slight adjustments within therich or lean mixture regimes. Algorithms operating in one or moreprocessors may operate to make such changes.

In some embodiments, the method further comprises repeating the steps ofthe method to redetermine the maximum-power AFR fiducial (960). Whenoperating conditions change in a significant degree (e.g., moresignificant changes in the parameters noted above) it may be advisableto repeat the steps 910-950 to re-establish an accurate maximum-powerAFR fiducial.

FIG. 10 is a flowchart providing greater detail on the step 820 of FIG.8 of how to determine the maximum-efficiency AFR fiducial. The method isimplemented for an ICE initially operating at steady-state, constantload conditions at an arbitrary (possibly unknown) AFR. The methodincludes the step 1010 of increasing the AFR (i.e., decreasing theamount of fuel delivered per stroke relative to the amount of air) anddetermining (1020) any change in the absolute amount of fuel injectedfor each intake stroke.

If the absolute amount of fuel injected for each intake stroke at thedetermining step 1020 is observed to decrease (1027) as the ICE speedcontroller maintains the ICE at a constant rpm, the method comprises(1040) again increasing the AFR (i.e., decreasing the relative amount offuel), determining a change in the absolute amount of fuel injected foreach intake stroke, and repeating the increase 1040 in AFR anddetermination of a change in the absolute amount of fuel injected perstroke until the absolute amount of fuel injected for each intake strokeincreases in response to the increase in AFR. The maximum-efficiency AFRis the AFR at which any further increase in AFR results an increase inthe absolute amount of fuel injected per stroke. Stated differently, themaximum-efficiency AFR is the AFR at which the absolute amount of fuelrequired to maintain the ICE rotational speed is minimized.

Returning the determination step 1020, if the absolute amount of fuelinjected for each intake stroke was observed to increase (1025) inresponse to the increase in AFR at step 1010, the method comprisesdecreasing (1030) the AFR and determining a change in the absoluteamount of fuel injected in response to the decrease in AFR. If theabsolute amount of fuel injected for each intake stroke decreases inresponse to the AFR decrease in step 1030, the method comprisesrepeating the step 1030 of decreasing the AFR and determining a changein the absolute amount of fuel injected for each intake stroke until theabsolute amount of fuel injected for each intake stroke increases inresponse to a decrease in AFR. The maximum-efficiency is the AFR atwhich any further decrease in AFR results in an increase in the absoluteamount of fuel injected for each intake stroke. As with step 1040, themaximum-efficiency AFR is the AFR at which the absolute amount of fuelper stroke required to maintain the ICE at its controlled rotationalspeed is minimized.

In some embodiments, the method further comprises (1050) storing orlogging the control parameters (e.g., the fraction of a full strokevolume of fuel from a pump and/or the amount of air inducted for eachintake stroke) that achieves the minimum-power AFR. When operatingconditions change during the operation of the ICE (e.g., based operatingparameters such as acceleration or deceleration requests, engine load,intake air temperature, intake air humidity, intake air pressure,altitude, engine running duration, engine temperature, engine rotationalspeed, fuel quality, or other inputs received from system statusmonitoring sensors, the method may include changing the target AFR tocause the fuel metering system to switch between a stoichiometricmixture, a rich mixture, and a lean mixture, or to make slightadjustments within the rich or lean mixture regimes. Algorithmsoperating in one or more processors may operate to make such changes.

In some embodiments, the method further comprises repeating the steps ofthe method to redetermine the maximum-efficiency AFR fiducial (1060).When operating conditions change in a significant degree (e.g., moresignificant changes in the parameters noted above), steps 1010-1050 maybe repeated to re-establish an accurate maximum-efficiency AFR fiducial.

Once the maximum-power and maximum-efficiency fiducials are known, theICE may be operated at any desired AFR by controlling the amount of fueldelivered into the combustion chamber for each intake stroke (using,e.g., the FME controller) based on interpolation or extrapolation fromthe two fiducials. In addition, although the steps of determining achange in engine power output in response to increases or decreases inAFR when determining the maximum-power AFR fiducial can be performed inone embodiment based on a single intake stroke, in some embodiments thechange in power output is determined over several engine cycles (e.g.,2, 5, 10, 50, or 100 or more intake cycles), and a measure of centraltendency for the power output over those cycles is used as the powerchange. Similarly, although the steps of determining a change in theabsolute amount of fuel injected or delivered to the combustion chamberin response to increases or decreases in AFR when determining themaximum-efficiency AFR fiducial can be performed based on a singleintake stroke, in some embodiments the change in absolute amount of fuelis determined over several engine cycles and a measure of centraltendency for absolute amount of fuel injected is used as the change infuel injected.

In one embodiment, the invention comprises a method of controlling theAFR of an operating ICE without sensing chemical composition (e.g., O₂concentration) of the exhaust gas of the ICE. The method may comprisedetermining one or both of the maximum-power and maximum-efficiency AFRfiducials, which may be used to control the amount of fuel delivered foreach intake stroke of the ICE without determining the chemicalcomposition of the exhaust gases.

In another embodiment, the invention comprises a method of controllingthe AFR of an operating ICE without sensing or otherwise determining thetemperature of the exhaust gas of the ICE. The method may comprisedetermining one or both of the maximum-power and maximum-efficiency AFRfiducials, which may be used to control the amount of fuel delivered foreach intake stroke of the ICE without determining the chemicalcomposition of the exhaust gases.

In some embodiments, the method comprises determining a change in poweroutput of the ICE in response to a change in AFR based on a change inengine rotational speed in response to the change (i.e., increase ordecrease) in AFR. In some embodiments, the change in power output inresponse to a change in AFR is based on a change of throttle positionimplemented by the ICE speed controller in response to a change in AFR(e.g., implemented by a fuel metering element controller).

In one embodiment of the invention power fiducial is determined byidentifying one of 1) the throttle position corresponding to thesmallest amount of air inducted at which the ICE speed controller canmaintain a constant speed under conditions of constant load, and 2) theminimum amount of air inducted into the ICE at which the speedcontroller can maintain a constant speed under conditions of constantload.

In some embodiments, decreasing the AFR may be performed by at least oneof decreasing the amount of air inducted into the ICE and increasing theamount of fuel injected into the ICE for each induction stroke. In someembodiments, increasing the AFR may be performed by at least one ofincreasing the amount of air inducted into the ICE and decreasing theamount of fuel injected into the ICE for each induction stroke.

In some embodiments, determining a power output of the ICE at aparticular AFR setting comprises determining a measure of centraltendency of the power output at the AFR setting for a plurality ofengine cycles, and determining a change in power output after a changein AFR includes comparing the measure of central tendency of the poweroutput before the change to the measure of central tendency of the poweroutput after the change in AFR.

In one embodiment, the invention comprises a non-transitorycomputer-readable medium storing code for execution by a processor toperform a method of controlling the AFR of an operating ICE. The methodmay be a method that includes determining one or more of a maximum-powerAFR fiducial and a maximum-efficiency AFR fiducial as described inconnection with the FIGS. 8-19 and the foregoing paragraphs.

In some embodiments, the invention comprises a method of controlling theAFR of an operating ICE based on at least one of the maximum-power AFRfiducial and the maximum-efficiency AFR fiducial and on a slope of apower vs AFR curve for the ICE. Referring again to FIG. 1, it isapparent that the power-AFR curve 110 has a smooth andcontinuously-varying slope that includes positive slope values (e.g., onthe left side of the maximum-power AFR point 115), and negative slopevalues (e.g., on the right side of the maximum-power AFR point 115).Because the slope of the curve is continuously-varying, each data pointon the curve is characterized by a unique slope value. Accordingly, anypoint on the curve may be determined with knowledge of the slope of thepower-AFR curve when operating the ICE at an unknown AFR and itsdistance (X-axis) from one of the maximum-power AFR fiducial and themaximum-efficiency AFR fiducial.

In one embodiment, method involves characterizing at least a portion ofthe power performance of the ICE, determining one of the maximum-powerand maximum-efficiency AFR fiducials, and operating the ICE at a desiredAFR based on the maximum-power or maximum-efficiency AFR fiducials andthe power output of the ICE in the region of the desired AFR.Characterizing a portion of the power performance of the ICE maycomprise creating (e.g., by operating the ICE at a plurality of AFRvalues that include both lean and rich AFR values (and preferably leanAFR values in excess of 15.4 and rich AFR values less than 12.6) anddetermining the power output of the ICE for a plurality engine cycles ateach AFR in the plurality of AFR values. Characterizing a portion of thepower performance of the ICE may also comprise accessing or receiving aknown power-AFR curve for the ICE and using the power-AFR curve todetermine a slope (i.e., rate of change of power) for a candidate AFR byoperating the ICE at a plurality of AFR settings near the candidate AFR.Determining the power output of the AFR in the region of candidate AFRin one embodiment comprises determining the slope of the power-AFR curvefor the ICE at (or near) the candidate AFR by operating the ICE at oneor more AFR values in close proximity to the candidate AFT anddetermining a rate of change of power for the candidate AFR (e.g., alocal slope of the AFR-power curve). With knowledge of the fuel amountand air inducted at one of the AFR fiducials, the system may determinethe actual AFR of the candidate AFR by comparing the experimentallydetermined power slope behavior for the candidate AFR to the slope ofthe known or determined AFR curve. If the candidate AFR is not thedesired AFR value, the system may adjust one or more of the air inductedor fuel delivered for each intake stroke to operate the ICE at thedesired AFR.

FIG. 11 illustrates an example relationship between the IdPI measuredmetric and a prescribed fuel output variable (pulse width of the pumpstroke control signal in the illustrated case). The engine'sinstantaneous operating speed (RPM) is determined by monitoring the IdPIpressure sensor signal, rotation of the engine's shaft, or other methodsknown in the art. For every intake stroke, a value for IdPI is obtainedas given on the X-axis. During configuration of the specific engine,bench testing determines the relationship between the IdPI variable andthe prescribed fuel output variable necessary to achieve a goal AFR.Fuel pump pulse width of the MLP is given here for an exemplary enginefor illustrative purposes only. In a preferred embodiment, therelationships may be represented by equations (shown in FIG. 5 for twoexample curves) simply calculable by one or more Logic Units (e.g., 540,760). In a preferred embodiment, slight adjustments (‘trims’) may beaccomplished by adjusting only one or a few variables of the equationsof FIG. 11. For example, adjusting the value of the constant having avalue of 700 for the 1800 RPM curve of FIG. 11 effectively moves thecurve upward/downward, while adjusting the exponential constant having avalue of 0.002 in the 3600 RPM curve effectively increases/decreases the‘steepness’ of the curve. In an alternate embodiment, the Logic Unit(s)(540, 760) may include a lookup table of pre-determined values of one ormore input variables (e.g., RPM, IdPI, load metric, temperature, runningduration, etc.) and perform a look-up of the necessary fuel deliveryoutput variable to best-match the pre-determined values in the lookuptable(s).

Noteworthy from FIG. 1, if the preferred operating point is lean-of-peakpower, such as best efficiency 15.4:1, the operating point exists on a‘slippery slope’ of power vs lean AFR. This is especially problematicwhen operating on a steep part of the lean slope, and the throttle valveis opened unexpectedly. The opening of the throttling valve allows moreair into the cylinder and thus can cause AFR to become even more lean,resulting in an even lower power point on the AFR/power curve. If thiscascading effect proceeds for more than a few engine strokes (e.g. formore than a fraction of a second), this can cause lean flame-out/theengine to stop running abruptly upon opening of the throttling valve. Toovercome this problem, embodiments of the invention may implement atechnique of “acceleration enrichment.” In this invention, we may applya steeper slope to the curve (dashed-line in FIG. 11) at a point justbeyond the steady-state operating point which causes any given IdPIvalue to be prescribed more fuel than would normally be prescribed, thusenriching the mixture beyond the pre-determined values that would beobtained by using the equation unmodified. The location of theinflection point is calculated and adapted to be just beyond the presentIdPI operating point such that an immediate wider-opening of thethrottling valve is met with a fuel mixture which is more enriched thanwould otherwise be prescribed with steady-state running. Meeting anabrupt throttle opening with a slightly enriched mixture causes theoperating point to increase on the power curve, thus aiding the engineto increase its output as is the request by increasing the throttleopening.

Also noteworthy from FIG. 1 is that the system of the invention canaffect power delivery without access to the throttling valve bymanipulating the AFR at any given throttling valve position. This givesa benefit of reduced system cost and easier integration with existingdesigns. If for example the steady-state operating point is chosen to bebest efficiency AFR of 15.4:1, then the LEFM system may affect morepower at the present throttle opening setting by instantly delivering anAFR with more power e.g. 12.8:1. From this control authority arises theability to dampen/control harmonic/hunting-fluctuations in throttle andengine rpm common with mechanically-controlled governors. Further, ifthe engine is loaded to such an extent that it cannot maintain goal rpmat a lean AFR, the LEFM may be programmed or commanded to enrich toprovide more power—up to a maximum power AFR of 12.8:1 AFR. In this way,the LEFM invention may affect the benefits of computer-controlled logicto the existing mechanically-controlled designs with no additional costssince these benefits arise from an added behavior in software, whoseadditional manufacturing cost is zero due to the nature of softwareduplication manufacturing operations.

The advantages of the present invention include, without limitation, thebenefits which can arise from using software logic to adapt air-fuelratio metering and control in an internal combustion engine.

In broad embodiment, the present invention is an apparatus to mix fuelinto the air intake of an internal combustion engine.

In various embodiments, the present invention relates to the subjectmatter of the following numbered paragraphs.

201. A fuel metering system for an internal combustion engine (ICE), theICE having a maximum power output, at least a first combustion chamberassociated with at least a first cylinder, and at least an intake strokeand a combustion stroke, the fuel metering system comprising:

a fuel injection timing unit providing a first timing signal indicativeof the occurrence of at least one timepoint during an intake stroke;

a fuel metering element (FME) having a predetermined full stroke volumefor metering fuel into an air-fuel mixing location in the ICE during theintake stroke, wherein the predetermined full stroke volume is a volumeof fuel creating one of a rich, combustible fuel mixture and astoichiometric fuel mixture in the at least a first combustion chamberof the ICE at maximum ICE power output; and

a FME controller operatively coupled to the FME to control the deliveryof fuel to the air-fuel mixing location in response to the first timingsignal, and to control the stroke volume of the FME to deliver one of afull stroke volume of fuel and a fraction of a full stroke volume offuel to achieve a desired AFR.

202. The fuel metering system of numbered paragraph 201, wherein thefuel injection timing unit comprises circuitry adapted to receive atleast one ICE timing signal indicative of the occurrence of at least oneof an intake stroke of the ICE, a compression stroke of the ICE, acombustion stroke of the ICE, and an exhaust stroke of the ICE, and toprovide the first timing signal based on the at least one ICE timingsignal.

203. The fuel metering system of numbered paragraph 202, wherein the atleast one ICE timing signal is provided by a sensor selected from acamshaft position sensor, a crankshaft position sensor, and an engineoutput shaft position sensor.

204. The fuel metering system of numbered paragraph 201, wherein thefuel metering element (FME) comprises at least one of a valve and apump.

205. The fuel metering system of numbered paragraph 201, furthercomprising:

a power determination unit for determining at least one of a poweroutput and a change in power output of the ICE for a plurality of enginecombustion cycles at each of a plurality of AFR values; and

an AFR fiducial determination unit for determining at least one of amaximum-power AFR fiducial value and a maximum fuel-efficiency fiducialvalue based on the determined at least one of a power output and achange in power output at each of the plurality of AFR values, whereinthe AFR fiducial determination unit causes the FME controller to operatethe ICE for the plurality of engine combustion cycles at each of theplurality of AFR values.

206. The fuel metering system of numbered paragraph 205, wherein the ICEcomprises a speed controller to adjust a throttle to maintain the ICE ata constant rotational speed in response to changes in load and poweroutput, the fuel metering system further comprising:

an air induction determination unit (AIDU) to determine an at least oneof an amount of air and an amount of oxygen inducted into the at least afirst combustion chamber of the ICE for each intake stroke.

207. The fuel metering system of numbered paragraph 205, wherein thedesired AFR is determined by one of interpolation and extrapolation fromthe at least one of a maximum-power AFR fiducial value and a maximumfuel-efficiency fiducial value.

208. The fuel metering system of numbered paragraph 201, wherein thefuel injection timing unit comprises:

at least one positioning element on a moving part of the enginecomprising one of a cam and a magnet; and

a positioning element sensor comprising one of a mechanical contactelement and a magnetic field sensor for sensing each time the at leastone positioning element passes the sensor.

209. The fuel metering system of numbered paragraph 201, wherein thefuel injection timing unit is adapted to determine a plurality oftimepoints, wherein at least one timepoint of the plurality oftimepoints is indicative of the occurrence of an intake stroke for eachcylinder in the ICE.

210. The fuel metering system of numbered paragraph 201, wherein thefirst timing signal is indicative of the start of an intake stroke.

211. The fuel metering system of numbered paragraph 201, wherein thefuel injection timing unit is adapted to provide a plurality oftimepoints during the occurrence of the intake stroke.

212. The fuel metering system of numbered paragraph 201, furthercomprising:

power generator circuitry adapted to harvest power from at least onemoving component of the ICE, wherein the power generator circuitryprovides power to at least one of the fuel injection timing unit, theFME, and the FME controller.

213. The fuel metering system of numbered paragraph 212, wherein the FMEcomprises a pump comprising:

a pump inlet coupled to a fuel source;

a pump outlet coupled to a delivery conduit having a distal end at theair-fuel mixing location;

a fuel metering chamber having a predetermined volume;

an actuating element movable between a first position associated with aminimum volume in the fuel metering chamber and a second positionassociated with a maximum volume in the fuel metering chamber, thedifference between the minimum and maximum volumes associated with thepredetermined full stroke volume for metering fuel into an air-fuelmixing location in the induction conduit; and

a coil coupled to said power generator circuitry, the actuating element,and the FME controller;

wherein the coil and said power generator circuitry are sized to causethe FME to deliver a fraction of a full stroke volume providing a richfuel mixture during a startup condition of the ICE when the FMEcontroller is not operating to control the delivery of fuel to theair-fuel mixing location and to control the stroke volume of the FME.

214. The fuel metering system of numbered paragraph 213, furthercomprising switching circuitry to ensure that during non-startupconditions, the FME controller controls the delivery of fuel to thefuel-air mixing location and the stroke volume of the FME.

215. The fuel metering system of numbered paragraph 213, furthercomprising:

a fuel supply conduit having a first end coupled to a fuel source and asecond end coupled to the pump inlet;

wherein the fuel metering system comprises a sealed system having noopening to the atmosphere from the proximal end of the fuel supplyconduit to the pump outlet.

216. The fuel metering system of numbered paragraph 215, wherein thefuel metering system comprises a sealed system having no opening to theatmosphere from the proximal end of the fuel supply conduit to theair-fuel mixing location.

217. The fuel metering system of numbered paragraph 201, wherein thefuel injection timing unit and the FME controller comprise a singleprocessor.

218. The fuel metering system of numbered paragraph 201, furthercomprising:

an air induction determination unit (AIDU) adapted to determine at leastone of an amount of air and an amount of oxygen inducted into the atleast a first combustion chamber during at least a plurality of intakestrokes of the ICE, the AIDU comprising

-   -   a pressure sensor to sense one of absolute and differential        pressure associated with air inducted into the cylinder during        the at least a plurality of intake strokes, and to provide a        pressure signal indicative of the sensed one of absolute and        differential pressure; and    -   an induction change in pressure integration (IdPI) unit adapted        to determine one of absolute and differential pressure a        plurality of times during the at least a plurality of intake        strokes based on the pressure signal, and to determine the        amount of air inducted into the cylinder based on integrating        the pressures determined during the at least a plurality of        intake strokes.

219. The fuel metering system of numbered paragraph 218, wherein the FMEcontroller determines the one of a full stroke volume of fuel and afraction of a full stroke volume of fuel based on the amount of airinducted into the at least a first combustion chamber during the atleast a first intake stroke determined by the IdPI unit.

220. The fuel metering system of numbered paragraph 213, wherein thefuel system further comprises:

a fuel supply conduit having a first end coupled to a fuel source and asecond end coupled to the pump inlet;

wherein the fuel metering system has no flow restriction orifice fromthe first end of the fuel supply conduit to the air-fuel mixinglocation.

301. A fuel metering system for an internal combustion engine (ICE)comprising:

an air induction determination unit (AIDU) adapted to determine at leastone of an amount of air and an amount of oxygen inducted into a cylinderduring a first intake stroke of the ICE, the AIDU comprising:

-   -   a pressure sensor to sense one of absolute pressure and        differential pressure associated with air inducted into the        cylinder during the first intake stroke, and to provide a        pressure signal indicative of the one of absolute pressure and        differential pressure during the first intake stroke; and    -   an induction change in pressure integration (IdPI) unit adapted        to determine said one of absolute pressure and differential        pressure a plurality of times during the first intake stroke        based on the pressure signal, and to determine the amount of air        inducted into the cylinder based on integrating the plurality of        determinations during the first intake stroke;

a fuel metering element (FME) for metering fuel into an air-fuel mixinglocation in the ICE; and

a FME controller adapted to deliver fuel to the cylinder during theoccurrence of a second intake stroke, and to control the amount of fueldelivered to the cylinder during the second intake stroke based on thedetermined amount of air inducted into the cylinder during the firstintake stroke, to achieve a desired AFR.

302. The fuel metering system of numbered paragraph 301, wherein thefuel metering element (FME) comprises a predetermined full stroke volumefor metering fuel into the air-fuel mixing location, wherein thepredetermined full stroke volume is a volume of fuel creating a rich,combustible fuel mixture in the combustion chamber of the ICE, andwherein the FME controller is adapted to control the stroke volume ofthe FME to deliver one of a full stroke volume of fuel and a fraction ofa full stroke volume of fuel to achieve the desired AFR.

303. The fuel metering system of numbered paragraph 301, furthercomprising a fuel injection timing unit adapted to determine at least afirst timepoint indicative of the occurrence of at least one of thefirst intake stroke and the second intake stroke.

304. The fuel metering system of numbered paragraph 303, wherein thefuel injection timing unit determines the at least a first timepoint byreceiving a timing signal from at least one ICE sensor, the timingsignal indicative of the occurrence of at least one of an intake stroke,a compression stroke, a combustion stroke, and an exhaust stroke, andwherein the FME controller is adapted to deliver fuel to the cylinderduring the occurrence of the second intake stroke based on the timingsignal.

401. A fuel metering system for an internal combustion engine (ICE), theICE characterized by an intake stroke and a combustion stroke and havingan induction conduit with a proximal end fluid coupled to an oxygensource and a distal end coupled to at least one induction port of acombustion chamber, and a throttle operable between a first positionproviding a minimum amount of air to a combustion chamber and a secondposition providing a maximum amount of the air to the combustionchamber, the fuel metering system comprising:

an air induction unit adapted to determine at least one of an amount ofair and an amount of oxygen inducted into the combustion chamber throughthe induction conduit during at least a first intake stroke of the ICE,and to provide an air induction signal indicative of the at least one ofan amount of air and an amount of oxygen inducted into the combustionchamber during the at least a first intake stroke;

a fuel metering pump for metering fuel into an air-fuel mixing locationin the induction conduit during a second intake stroke of the ICE andcomprising:

-   -   a pump inlet coupled to a fuel source;    -   a pump outlet coupled to a fuel delivery conduit having a distal        end at the air-fuel mixing location;    -   a fuel metering chamber having a predetermined volume;    -   an actuating element movable between a first position associated        with a minimum volume in the fuel metering chamber, a second        position associated with a maximum volume in the fuel metering        chamber, and a third position between the first and second        positions and associated with an intermediate volume in the fuel        metering chamber, wherein the difference between the minimum and        maximum volumes is associated with a predetermined full stroke        volume for metering fuel into the air-fuel mixing location that        comprises a volume of fuel sufficient to provide a rich,        combustible fuel mixture in the combustion chamber of the ICE        during startup operation, and the difference between the minimum        and intermediate volumes is associated with a fraction of the        full stroke volume; and

a fuel metering pump controller adapted to cause the fuel metering pumpto deliver fuel to the fuel-air mixing location during the second intakestroke, wherein the fuel metering pump controller controls the strokevolume of the fuel metering pump based on the air induction signalindicative of the at least one of an amount of air and an amount ofoxygen inducted into the combustion chamber during the at least a firstintake stroke to deliver one of a full stroke volume of fuel and adesired fraction of the full stroke volume of fuel to achieve a desiredAFR during the second intake stroke.

402. The fuel metering system of numbered paragraph 401, wherein theinduction of the air and fuel in the induction conduit during the secondintake stroke occurs at no more than 2 psi above atmospheric pressure.

403. The fuel metering system of numbered paragraph 401 furthercomprising:

a fuel metering timing unit adapted to determine at least a firsttimepoint during the second intake stroke, wherein the fuel meteringpump controller initiates delivery of fuel from the fuel metering pumpto the fuel-air mixing locating during the second intake stroke at thefirst timepoint.

404. The fuel metering system of numbered paragraph 403, wherein thefuel metering timing unit determines at least the first timepoint duringthe second intake stroke based on the timing of the air inductionsignal.

405. The fuel metering system of numbered paragraph 403, wherein thefuel metering timing unit determines at least the first timepoint duringthe second intake stroke based on a signal from the ICE indicative ofthe occurrence of at least one of an intake stroke, a compressionstroke, a combustion stroke, and an exhaust stroke.

406. The fuel metering system of numbered paragraph 403, wherein thefuel metering timing unit determines at least the first timepoint duringthe second intake stroke based on a signal from at least one ICE sensorselected from a camshaft position sensor, a crankshaft position sensor,and an engine output shaft position sensor.

407. The fuel metering system of numbered paragraph 401, wherein theactuating element comprises at least one of a piston and a diaphragm,and wherein the actuating element is operable by a user to manuallycause delivery of fuel to the air-fuel mixing location.

408. The fuel metering system of numbered paragraph 401, wherein thefuel metering pump further comprises:

a coil coupled to an electrical energy source, wherein the coil whenenergized causes the actuating element to move between the firstposition and one of the second position and the third position based onthe electrical energy applied to the coil;

wherein the fuel metering pump controller is adapted to terminate theapplication of electrical energy to the coil to control the movement ofthe actuating element to a desired third position to cause the fuel pumpto deliver a desired fraction of a full stroke volume to the air-fuelmixing location to achieve a desired AFR.

409. The fuel metering system of numbered paragraph 408, furthercomprising:

a fuel supply conduit having a proximal end coupled to a fuel source anda second end coupled to the pump inlet;

wherein the fuel metering system comprises a sealed system having noopening to the atmosphere from the proximal end of the fuel supplyconduit to the pump outlet.

410. The fuel metering system of numbered paragraph 408, wherein thefuel metering system comprises a sealed system having no opening to theatmosphere from the proximal end of the fuel supply conduit to the fuelair-mixing location.

411. The fuel metering system of numbered paragraph 408, wherein thefuel metering pump further comprises a biasing element biasing theactuating element to the first position and preventing fuel delivery tothe air-fuel mixing locating when the ICE is operating at the idlethrottle position or not running.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.

All of the apparatus and methods disclosed and claimed herein may bemade and executed without undue experimentation in light of the presentdisclosure. While the invention has been described in terms ofparticular embodiments, it will be apparent to those of skill in the artthat variations may be applied to the apparatus and methods describedherein without departing from the concept, spirit and scope of theinvention, which are limited only by the claims.

What is claimed is:
 1. A fuel metering system for an internal combustionengine (ICE), the ICE having a maximum power output, at least a firstcombustion chamber associated with at least a first cylinder, and atleast an intake stroke and a combustion stroke, the fuel metering systemcomprising: a fuel injection timing unit providing a first timing signalindicative of the occurrence of at least one timepoint during at leastone of an intake stroke, a compression stroke, a combustion stroke, andan exhaust stroke of the ICE; a fuel metering element (FME) having apredetermined full stroke volume for metering fuel into an air-fuelmixing location in the ICE, wherein the predetermined full stroke volumeis a volume of fuel creating one of a rich, combustible fuel mixture anda stoichiometric fuel mixture in the at least a first combustion chamberof the ICE at the maximum power output; and a FME controller operativelycoupled to the FME to control the delivery of fuel to the air-fuelmixing location by providing an electrical control signal in response tothe first timing signal, wherein the electrical control signal causesthe FME to deliver one of a full stroke volume of fuel and a fraction ofa full stroke volume of fuel to achieve a desired air-to-fuel ratio(AFR).
 2. The fuel metering system of claim 1, wherein the fuelinjection timing unit comprises circuitry adapted to receive at leastone ICE timing signal indicative of the occurrence of at least one of anintake stroke of the ICE, a compression stroke of the ICE, a combustionstroke of the ICE, and an exhaust stroke of the ICE, and to provide thefirst timing signal based on the at least one ICE timing signal.
 3. Thefuel metering system of claim 2, wherein the at least one ICE timingsignal is provided by a sensor selected from a camshaft position sensor,a crankshaft position sensor, and an engine output shaft positionsensor.
 4. The fuel metering system of claim 1, wherein the fuelmetering element (FME) comprises at least one of a valve and a pump. 5.The fuel metering system of claim 1, further comprising: a powerdetermination unit for determining at least one of a power output and achange in power output of the ICE for a plurality of engine combustioncycles at each of a plurality of AFR values; and an AFR fiducialdetermination unit for determining at least one of a maximum-power AFRfiducial value and a maximum fuel-efficiency fiducial value based on thedetermined at least one of a power output and a change in power outputat each of the plurality of AFR values, wherein the AFR fiducialdetermination unit causes the FME controller to operate the ICE for theplurality of engine combustion cycles at each of the plurality of AFRvalues.
 6. The fuel metering system of claim 5, wherein the ICEcomprises a speed controller to adjust a throttle to maintain the ICE ata constant rotational speed in response to changes in load and poweroutput, the fuel metering system further comprising: an air inductiondetermination unit (AIDU) to determine an at least one of an amount ofair and an amount of oxygen inducted into the at least a firstcombustion chamber of the ICE for each intake stroke.
 7. The fuelmetering system of claim 5, wherein the desired AFR is determined by oneof interpolation and extrapolation from the at least one of amaximum-power AFR fiducial value and a maximum fuel-efficiency fiducialvalue.
 8. The fuel metering system of claim 1, wherein the fuelinjection timing unit comprises: at least one positioning element on amoving part of the engine comprising one of a cam and a magnet; and apositioning element sensor comprising one of a mechanical contactelement and a magnetic field sensor for sensing each time the at leastone positioning element passes the sensor.
 9. The fuel metering systemof claim 1, wherein the fuel injection timing unit is adapted todetermine a plurality of timepoints, wherein at least one timepoint ofthe plurality of timepoints is indicative of the occurrence of an intakestroke for each cylinder in the ICE.
 10. The fuel metering system ofclaim 1, wherein the first timing signal is indicative of the start ofan intake stroke.
 11. The fuel metering system of claim 1, wherein thefuel injection timing unit is adapted to provide a plurality oftimepoints during the occurrence of the intake stroke.
 12. The fuelmetering system of claim 1, further comprising: power generatorcircuitry adapted to harvest power from at least one moving component ofthe ICE, wherein the power generator circuitry provides power to atleast one of the fuel injection timing unit, the FME, and the FMEcontroller.
 13. The fuel metering system of claim 12, wherein the FMEcomprises a pump comprising: a pump inlet coupled to a fuel source; apump outlet coupled to a delivery conduit having a distal end at theair-fuel mixing location; a fuel metering chamber having a predeterminedvolume; an actuating element movable between a first position associatedwith a minimum volume in the fuel metering chamber and a second positionassociated with a maximum volume in the fuel metering chamber, thedifference between the minimum and maximum volumes associated with thepredetermined full stroke volume for metering fuel into an air-fuelmixing location in the induction conduit; and a coil coupled to saidpower generator circuitry, the actuating element, and the FMEcontroller; wherein the coil and said power generator circuitry aresized to cause the FME to deliver a fraction of a full stroke volumeproviding a rich fuel mixture during a startup condition of the ICE whenthe FME controller is not operating to control the delivery of fuel tothe air-fuel mixing location and to control the stroke volume of theFME.
 14. The fuel metering system of claim 13, further comprisingswitching circuitry to ensure that during non-startup conditions, theFME controller controls the delivery of fuel to the fuel-air mixinglocation and the stroke volume of the FME.
 15. The fuel metering systemof claim 13, further comprising: a fuel supply conduit having a firstend coupled to a fuel source and a second end coupled to the pump inlet;wherein the fuel metering system comprises a sealed system having noopening to the atmosphere from the proximal end of the fuel supplyconduit to the pump outlet.
 16. The fuel metering system of claim 15,wherein the fuel metering system comprises a sealed system having noopening to the atmosphere from the proximal end of the fuel supplyconduit to the air-fuel mixing location.
 17. The fuel metering system ofclaim 1, wherein the fuel injection timing unit and the FME controllercomprise a single processor.
 18. The fuel metering system of claim 1,further comprising: an air induction determination unit (AIDU) adaptedto determine at least one of an amount of air and an amount of oxygeninducted into the at least a first combustion chamber during at least aplurality of intake strokes of the ICE, the AIDU comprising a pressuresensor to sense one of absolute and differential pressure associatedwith air inducted into the cylinder during the at least a plurality ofintake strokes, and to provide a pressure signal indicative of thesensed one of absolute and differential pressure; and an inductionchange in pressure integration (IdPI) unit adapted to determine one ofabsolute and differential pressure a plurality of times during the atleast a plurality of intake strokes based on the pressure signal, and todetermine the amount of air inducted into the cylinder based onintegrating the pressures determined during the at least a plurality ofintake strokes.
 19. The fuel metering system of claim 18, wherein theFME controller determines the one of a full stroke volume of fuel and afraction of a full stroke volume of fuel based on the amount of airinducted into the at least a first combustion chamber during the atleast a first intake stroke determined by the IdPI unit.
 20. The fuelmetering system of claim 13, wherein the fuel system further comprises:a fuel supply conduit having a first end coupled to a fuel source and asecond end coupled to the pump inlet; wherein the fuel metering systemhas no flow restriction orifice from the first end of the fuel supplyconduit to the air-fuel mixing location.
 21. A fuel metering system foran internal combustion engine (ICE), the ICE having a maximum poweroutput, at least a first combustion chamber associated with at least afirst cylinder, and one or more engine strokes comprising an enginecycle, the fuel metering system comprising: a fuel injection timing unitproviding a first timing signal indicative of the occurrence of at leastone timepoint during said one or more engine strokes; a fuel meteringelement (FME) having a predetermined full stroke volume for meteringfuel into an air-fuel mixing location in the ICE during at least one ofthe one or more engine strokes, wherein the predetermined full strokevolume is a volume of fuel creating one of a rich, combustible fuelmixture and a stoichiometric fuel mixture in the at least a firstcombustion chamber of the ICE at maximum ICE power output; a FMEcontroller operatively coupled to the FME to control the delivery offuel to the air-fuel mixing location by providing an electrical controlsignal in response to the first timing signal, wherein the electricalcontrol signal causes the FME to deliver one of a full stroke volume offuel and a fraction of a full stroke volume of fuel to achieve a desiredair-to-fuel ratio (AFR); and power generator circuitry adapted toharvest power from at least one moving component of the ICE, wherein thepower generator circuitry provides power to at least one of the fuelinjection timing unit, the FME, and the FME controller.
 22. The fuelmetering system of claim 21, wherein the power generator circuitryprovides a first electrical signal that, in the absence of theelectrical control signal, causes the FME to deliver a full strokevolume of fuel, and wherein the FME provides an electrical controlsignal to regulate the first electrical signal to cause the FME todeliver a fraction of a full stroke volume of fuel.
 23. The fuelmetering system of claim 21, wherein the FME controller regulates thefirst electrical signal by shunting a portion of the first electricalsignal to reduce the stroke volume of the FME.
 24. A fuel meteringsystem for an internal combustion engine (ICE), the ICE having a maximumpower output, at least a first combustion chamber associated with atleast a first cylinder, and one or more engine strokes comprising anengine cycle, the fuel metering system comprising: a fuel injectiontiming unit providing a first timing signal indicative of the occurrenceof at least one timepoint during said one or more engine strokes; a fuelmetering element (FME) having a predetermined full stroke volume formetering fuel into an air-fuel mixing location in the ICE during atleast one of the one or more engine strokes, wherein the predeterminedfull stroke volume is a volume of fuel creating a rich, combustible fuelmixture in the at least a first combustion chamber of the ICE at maximumICE power output; a passive element causing the FME to initiate deliveryof a full stroke volume of fuel based on one of the first timing signal,engine rotation, or the occurrence of one of said one or more enginestrokes; and a FME controller operatively coupled to the FME adapted toreduce the delivery of fuel to the air-fuel mixing location to provideless than a full stroke volume by providing a shunting response to theoperation of the passive element, wherein in the absence of the shuntingresponse the FME delivers a full stroke volume of fuel.